Baltimore City State’s Attorney Ivan Bates announced charges have been filed against a suspect in the 2017 killing of an off-duty Washington D.C. Metropolitan Police sergeant. The charges were made possible through the newly created Cold Case Unit, a collaborative effort alongside Maryland and D.C. officials.

Dion Thompson has been charged with first-degree murder, conspiracy, and related charges in the November 2017 fatal shooting of Sgt. Tony Mason Jr. in west Baltimore. Mason was off-duty when he was gunned down five years ago.

“A cold case is still very much fresh in the hearts and minds of the victim’s family,” Bates stated. “My main job as State’s Attorney is holding offenders accountable, bringing closure for those impacted, and ensuring justice for Baltimore, the victims, and their loved ones.”

The charges against Thompson resulted from a thorough interagency investigation conducted by the Baltimore Police homicide unit, FBI, and Bureau of Alcohol, Tobacco, and Firearms. Bates commended the tireless efforts of prosecutor Kurt Bjorklund and the various law enforcement agencies involved.

Defined as unsolved criminal cases that remain open pending new evidence, cold cases had gone unresolved through traditional investigative means until now.

“For far too long, the details surrounding Sergeant Mason’s tragic death have remained a painful mystery,” said D.C. Police Chief Pamela Smith. “This arrest is a testament to the dedication of our law enforcement community and the collaborative efforts between agencies.”

Baltimore Police Commissioner Richard Worley stated the partnership with the Cold Case Unit allows them to “move cases forward and bring closure to victims’ families.” He hopes this case “puts perpetrators on notice” that they will be caught and held accountable.

While the charges are not a finding of guilt, Thompson is presumed innocent unless proven guilty at trial. The investigation aims to finally bring justice and closure to Mason’s loved ones five years after his untimely death.