Security is more than a profession for me—it's a passion. With over 15 years of experience in law enforcement, crisis response, and private security leadership, I've dedicated my career to protecting people, solving problems, and building teams that make a difference. As the Founder and CEO of Shield Defense Agency, I have the privilege of leading an incredible group of security professionals who share my commitment to service, integrity, and excellence.

Before launching Shield Defense Agency, I served with the St. Charles County Police Department, where I worked in patrol, investigations, crisis intervention, and hostage negotiations, earning several commendations along the way. I later transitioned into corporate security leadership, serving as Director of Security for Southern Glazer's Wine & Spirits and overseeing large-scale security operations and risk management programs.

When I'm not working, you'll usually find me spending time with family, supporting local businesses, enjoying life at the Lake of the Ozarks, or finding new ways to improve the services we provide to our clients. I firmly believe that great security starts with great people, honest communication, and a genuine desire to help others.

At the end of the day, my goal is simple: provide the highest level of protection and customer service possible while building lasting relationships with the people and communities we serve.

Protecting What Matters Most isn't just our slogan—it's the standard we live by every day. 🛡️

Mark Aschenbrenner brings more than two decades of leadership experience managing high-performance operations, large-scale teams, and mission-critical response environments. As Senior Vice President of Operations at Shield Defense Agency, Mark plays a key role in ensuring our clients receive exceptional service, seamless communication, and dependable security solutions every day.

Throughout his career, Mark has built and led operations centers supporting hundreds of personnel, coordinated real-time incident response efforts, and developed systems that improve efficiency, accountability, and communication. His ability to remain calm under pressure and lead teams through complex challenges makes him an invaluable asset to both our organization and our clients.

Prior to joining Shield Defense Agency, Mark spent over 20 years in enterprise operations leadership, where he successfully scaled operations teams, reduced response times, improved service delivery, and managed large-scale incident and disaster response programs. His experience directly translates to modern security operations, command center oversight, and client support services.

Outside of work, Mark enjoys spending time with family, mentoring team members, and finding innovative ways to improve operational excellence. He believes that strong relationships, clear communication, and a commitment to continuous improvement are the foundation of outstanding service.

At Shield Defense Agency, Mark's mission is simple: ensure every client receives the highest level of professionalism, responsiveness, and support while helping our teams perform at their absolute best.

"Great security starts with great leadership, exceptional communication, and a team that genuinely cares."

People are the foundation of every successful organization, and no one understands that better than Shelby Aschenbrenner. As Chief Human Resources Officer for Shield Defense Agency, Shelby leads our recruiting, employee development, compliance, and workforce strategy efforts, ensuring that we attract, develop, and retain the very best security professionals in the industry.

With extensive experience in talent acquisition, workforce planning, employee relations, and organizational development, Shelby has built a career around helping organizations grow through strong leadership and exceptional people. Her expertise in recruiting, onboarding, compliance, and employee engagement ensures that Shield Defense Agency maintains the high standards our clients have come to expect.

Before joining Shield Defense Agency's executive team, Shelby held leadership positions in talent acquisition and human resources with organizations including Lindenwood University, Quanta Services, and Charter Communications. Throughout her career, she has successfully managed large-scale hiring initiatives, workforce planning projects, and compliance-driven recruiting programs while partnering closely with executive leadership teams.

Shelby holds a Master's Degree in Human Resources and Employment Law and is passionate about creating a workplace culture where employees feel supported, valued, and empowered to succeed. Her commitment to professional development, accountability, and employee success helps ensure that every Shield Defense Agency team member is equipped to deliver exceptional service to our clients.

Outside of work, Shelby enjoys spending time with family, supporting community initiatives, and helping others achieve their personal and professional goals. She believes that when employees are given the tools, training, and support they need, they can accomplish extraordinary things.

"Great organizations are built by great people. My goal is to help every member of our team reach their full potential while delivering exceptional service to those we protect."

Lisa Aschenbrenner serves as the Director of Sales and Strategic Partnerships for Shield Defense Agency, where she leads business development initiatives, cultivates strategic relationships, and drives growth opportunities that support the company's mission of providing professional, reliable security services.

With more than 25 years of experience in sales, customer relations, and business development, Lisa has built a reputation for creating meaningful partnerships, identifying new market opportunities, and delivering results through a relationship-focused approach. Her ability to connect with clients, understand their unique needs, and develop tailored solutions has been a cornerstone of her professional success throughout her career.

At Shield Defense Agency, Lisa is responsible for expanding the company's presence across commercial, hospitality, residential, and government sectors. She works closely with clients, community stakeholders, and industry partners to develop long-term relationships that strengthen Shield's reputation as a trusted security provider. Her efforts help ensure the organization continues to grow while maintaining the high standards of service and professionalism that define the company.

Lisa's expertise includes business development, strategic partnerships, client relationship management, contract negotiations, marketing strategy, and revenue growth. She is passionate about building strong connections, creating value for clients, and supporting initiatives that contribute to the success of both the organization and the communities it serves.

As a member of Shield Defense Agency's leadership team, Lisa plays an integral role in advancing the company's strategic objectives and identifying opportunities for continued expansion. Her commitment to excellence, collaborative leadership style, and dedication to client success make her a valuable asset to the organization and its partners.

When she's not working, Lisa enjoys spending quality time with her family, traveling to new destinations, diving into a good book, and creating lasting memories with her grandchildren. Whether she's exploring a scenic hiking trail, planning her next adventure, or simply enjoying time with loved ones, she values the relationships and experiences that enrich both her personal and professional life. Her passion for connecting with people extends beyond the workplace and reflects the warmth, dedication, and authenticity she brings to everything she does.

“I’ve always believed that the strongest partnerships begin with genuine relationships, built on trust, communication, and a shared commitment to success.”

Austin Edgar joined Shield Defense Agency with a foundation built on service, leadership, and a commitment to protecting others. Drawing from his military and law enforcement background, Austin brings a calm, professional presence and a mission-focused mindset to every client interaction and operational challenge.

A former U.S. Army Sergeant, Austin served six years as both a Chemical, Biological, Radiological, and Nuclear (CBRN) Specialist and a Black Hawk Helicopter Crew Chief, where he developed expertise in risk assessment, emergency response, operational planning, and leadership under pressure. His military service instilled the discipline, accountability, and attention to detail that continue to define his professional approach today.

Following his military career, Austin continued serving his community in law enforcement, first as a patrol officer and later as a narcotics investigator assigned to a multi-jurisdictional drug task force supported by state and federal grants. In that role, he worked closely with agencies including the DEA, local law enforcement partners, and federal task force personnel. These experiences strengthened his abilities in crisis management, threat assessment, de-escalation, investigations, and building strong partnerships across diverse organizations.

As Regional Operations and Business Developement Manager for Shield Defense Agency, Austin oversees daily security operations, personnel management, client relations, training initiatives, and service delivery across multiple accounts. He is passionate about developing security professionals, maintaining exceptional client communication, and ensuring every Shield Defense Agency client receives reliable, proactive, and professional protection. Austin firmly believes that effective security is built on trust, visibility, communication, and a genuine commitment to the people and organizations we serve.

His extensive background in military operations, law enforcement, and security leadership allows him to understand security challenges from multiple perspectives. Whether coordinating personnel for a large-scale event, assisting clients with safety concerns, managing emergency situations, or mentoring security professionals in the field, Austin approaches every situation with professionalism, integrity, and a solutions-oriented mindset.

Outside of work, Austin enjoys spending time with his family, riding motorcycles, enjoying the outdoors, gaming, and building custom computers. His approachable personality, leadership experience, and dedication to helping others make him a valued leader within Shield Defense Agency and a trusted partner to the clients and communities we protect.

“Protection is more than a service, it’s a commitment. Every client, every employee, and every community we serve deserves professionalism, accountability, and a security partner they can trust.”

Shield Defense Agency is proud to partner with Dr. Buster Lackey, PhD, LPC-S, CIT-C, an independent behavioral health consultant and nationally recognized leader in behavioral health, crisis response, and public safety wellness. With more than two decades of combined experience in mental health, substance abuse treatment, law enforcement, emergency services, and crisis intervention, Dr. Lackey brings an unmatched level of expertise to our organization.

Dr. Lackey’s distinguished public safety background includes service as an elected County Constable, Chief Deputy Coroner, and frontline Fire/EMS responder. These experiences have provided him with a unique understanding of the psychological demands placed upon law enforcement officers, security professionals, first responders, and those tasked with protecting others.

In addition to his extensive field experience, Dr. Lackey serves as a Behavioral Health Consultant for the FBI’s Crisis Negotiation Unit, providing clinical insight and psychological support during high-risk and critical incidents. He has also assisted numerous local, state, and federal agencies in developing wellness initiatives and behavioral health programs designed to strengthen organizational resilience and support personnel throughout their careers.

As an independent consultant partnered with Shield Defense Agency, Dr. Lackey provides comprehensive psychological evaluation services for individuals seeking armed security assignments within our organization. His role includes conducting professional psychological assessments designed to evaluate an individuals suitability for armed security responsibilities, helping ensure our armed personnel possess the judgment, emotional stability, decision-making ability, and resilience necessary to safely and professionally perform their duties.

Additionally, Dr. Lackey serves as a trusted advisor to Shield Defense Agency’s leadership team on officer wellness, crisis response, trauma-informed practices, resilience training, and employee support initiatives. His expertise helps strengthen our commitment to maintaining a professional, healthy, and prepared workforce capable of responding effectively in high-pressure environments.

A respected author, keynote speaker, educator, and media contributor, Dr. Lackey is widely recognized for his ability to translate complex behavioral health concepts into practical guidance for public safety professionals. His commitment to developing resilient, capable, and emotionally healthy professionals aligns directly with Shield Defense Agency’s mission of delivering exceptional security services to our clients.

Through our partnership with Dr. Lackey as an independent behavioral health consultant, Shield Defense Agency further reinforces its commitment to professionalism, accountability, officer wellness, and public safety by ensuring that personnel entrusted with carrying firearms are held to rigorous psychological standards and supported throughout their careers.

"The responsibility of carrying a firearm in a professional capacity extends far beyond marksmanship and training—it requires sound judgment, emotional resilience, ethical decision-making, and the ability to remain composed under pressure. My role is to help ensure that those entrusted with protecting others possess the psychological readiness necessary to perform that responsibility safely, professionally, and with integrity. I am proud to partner with Shield Defense Agency, an organization that recognizes the importance of investing in both the wellness and preparedness of its personnel."