402: Brian O’Hare and Sean O’Brien - Chattanooga Terrorist Attack, ERT Crime Scene

In this episode of FBI Case File Review, retired agent Brian O’Hare and former Chattanooga Police Lieutenant Sean O’Brien review the July 16, 2015, attack by lone terrorist Muhammad Youssef Abdulazeez, who opened fire on two military installations in Chattanooga, Tennessee. He first committed a drive-by shooting at a recruiting center, where one Marine was injured by gunfire. He then traveled to a U.S. Navy Reserve center where he continued firing and was killed by police during the gunfight.

Four U.S. Marines were shot and killed at the scene, and one U.S. Navy sailor died at a hospital two days later. A police officer was wounded.

Special Agent (Retired)

Brian O’Hare

9/1999 – 9/2023

Brian O’Hare served in the FBI for 24 years. His first assignment was to the Knoxville Division, where he worked both national security and criminal matters. He was promoted to a supervisory position at FBI Headquarters, Counterterrorism Division.

After completing his headquarters assignment, he returned to the Knoxville division, Johnson City RA, where, in addition to his cases, Brian was a member and team leader on the Evidence Response Team for most of his FBI field career, using his forensic skills to collect evidence at some of the Bureau’s most challenging crime scenes. Later in his Bureau career, Brian served on the Victim Services Response Team, deploying to mass casualty events to support victims and families.

His peers elected him President of the FBI Agents Association (2019–2023), where he advocated for agents’ safety, resources, and professional development nationwide. Support the FBIAA’s two charitable funds, the Memorial College Fund and the Membership Assistance Fund, by texting FBIAA to 50155 or visit the FBIAA Ways to donate page.

Brian currently serves as a Civil Service Commissioner for Police and Fire in Johnson City, Tennessee, where he helps steward fair hiring, promotion, and disciplinary processes that strengthen public trust and departmental excellence. He began his law enforcement career with the Conroe Police Department in Texas and is a graduate of the FBI National Academy (Session 196).

Chief Sean O’Brien

As Associate Vice Chancellor for Public Safety and Chief of Police at the University of Tennessee Chattanooga, Sean leads a full public safety division serving an urban campus of over 14,000 students, faculty, and staff. This involves oversight of the UTC Police Department, Environmental Health & Safety, and Emergency Management, fostering a culture of safety and collaboration.

With over 30 years of experience in law enforcement, public safety, and leadership, Sean has held key positions with the Chattanooga Police Department and the New Jersey State Police, specializing in crisis management, homeland security coordination, and intelligence-led policing. His career includes commanding operational units, developing advanced threat mitigation strategies, and integrating technologies, including AI, to increase safety capabilities.

Sean is passionate about building strong partnerships across local, state, and federal agencies. He has worked closely with organizations such as the FBI, Tennessee Homeland Security, and the Hamilton County Office of Emergency Management, among many others. His leadership experience has extended beyond policing to include organizational governance, having served as the President of the Fraternal Order of Police in Chattanooga and contributed to initiatives that saved Chattanooga millions in pension costs and improved equity in pay and promotions.

Sean has received honors including Officer of the Year, the Medal of Valor, and the NACOP Top Cop Award.