Sergeant Dunne served as a U.S. Marine before his 27 year police career. He served as a SWAT Officer and sniper for 8 years, and also a full time academy instructor for 8 years. He is highly decorated, to include the Police Medal of Honor, the Distinguished Service Cross, and multiple life-saving awards. He has been a pistol, rifle, and shotgun instructor since 1999, and has taught firearms, self-defense, tactical combat casualty care, and active shooter response, to thousands of military, civilians, and Law Enforcement nationally. Sergeant Dunne was the lead firearms and combatives instructor for the Steel Curtain contract, client: U.S. Intelligence. Sergeant Dunne is certified as an expert witness in federal court in firearms, edged weapons, & self-defense. Sergeant Dunne was a subject matter expert for Colorado POST, (Peace Officer Standards and Training,) for 13 years, many of those years as the SME Chair. In that capacity he reported directly to the State Attorney General regarding Police training. He has competed as both an amateur and professional in MMA, boxing, and kickboxing, and has been shooting competitively for over 20 years. Sergeant Dunne is a Colorado Police Combat Pistol Champion. Sergeant Dunne is the lead firearm’s instructor for a large urban multi-jurisdiction police academy. Besides training, he provides executive protection for many high worth individuals, to include NFL owners, celebrities, and foreign royalty.  Sergeant Dunne founded Ragnar Tactical in 2002, and teaches year round. He published his memoirs, “The Jagged Blue Line”, in 2024.