From ‘painful mystery’ to arrest: New cold case unit charges man in 2017 murder of off-duty DC officer

A Baltimore County man is accused of murdering an off-duty D.C. police officer found shot in Baltimore City in November 2017, in what city prosecutors say will be the first case handled by a newly established cold case unit.

Dion Thompson, who is currently being held in federal prison in New Jersey, faces charges in Baltimore City Circuit Court for the killing of Tony Mason Jr., 40, a Metropolitan Police Department officer in Washington. Baltimore Police say in charging documents that he is believed to be “one of the two shooters” in Mason’s slaying. A female passenger in the car with Mason also was wounded by gunfire.

Metropolitan Police Chief Pamela Smith said at a news conference Wednesday that Mason’s death in West Baltimore had been a “painful mystery” for years, but, because of a “brave person” who called in a tip and detectives who “never stopped” working, there now could be some closure.

“While we cannot ease the pain and the loss, or the memories of that day, we can take solace in the fact the person responsible is being brought to justice,” Smith said.

Officials said Wednesday they believe “other people” who have not been apprehended also were “involved,” and encouraged additional tips.

“You may think that you’ve gotten away with murder,” Baltimore City State’s Attorney Ivan Bates said. “But [with] advances in technology and us working together, we’re going to make sure we focus on holding you accountable.”

The break in Mason’s homicide case came in early 2023 when a person called in a tip, according to court documents. The tipster was not an eyewitness to the killing but said they were close to someone who confessed that he and two others had killed a D.C. police officer.

Information the tipster provided was corroborated and led investigators to a potential suspect, said Assistant State’s Attorney Kurt Bjorkland, who will be the city prosecutor assigned to Bates’ new cold case unit.

Bjorkland said Wednesday he couldn’t comment on a motive, any link between Thompson and Mason, or whether this was a case of mistaken identity. He also said he wasn’t able to say whether any reward money had been awarded. Charging documents in the case say the tipster is “aware” of rewards being offered but “has never asked to receive the benefit.”

Thompson faces nearly two dozen charges in Baltimore City District Court including first- and second-degree murder, first- and second-degree assault and handgun offenses, according to charging documents provided by the State’s Attorney’s Office.

The case did not appear in online court records, as of Wednesday afternoon. An attorney for Thompson in a federal criminal case said he was not currently representing him.

According to the tipster’s account, laid out by police in court records, Thompson was leaving a Baltimore residence in 2017 when he saw a dark vehicle parked outside and became paranoid. He told two people he was with, “Man-Man” and “Chub,” not to come outside because he suspected the people in the car were there to rob him or to retaliate against him for robberies he’d committed. He then told “Man-Man” and “Chub” to get guns, according to the charging documents.

When Thompson returned to the residence, he picked up the other two in a vehicle and they circled the block. Charging documents state that “the intention was to shoot up the parked vehicle.”

As soon as the man in the parked car looked up, they fired weapons. Thompson told the tipster he “emptied his clip” into the car. The three men then fled the scene and Thompson dropped off the other two off elsewhere, according to charging documents.

Later that night, he reportedly told his brother that he needed more bullets and that he’d “got one tonight,” referring to killing someone.

“I got one tonight, dummy,” Thompson reportedly told his brother. “Watch the news.”

He later learned from news reports that he’d killed an off-duty police officer and that there was a woman passenger in the vehicle, according to charging documents.

Mason was found in the 2800 block of Elgin Avenue in West Baltimore’s Panway/Braddish Avenue neighborhood along Gwynns Falls Parkway.

The tipster also said Thompson had given them information about the identities of “Man-Man” and “Chub.” Police used those details to identify “Man-Man” as Jerard Walker, who died in a vehicle crash in 2018. “Chub,” meanwhile, was said to be “on the street.” His identity is redacted.

Police wrote that the tipster gave two interviews to police, and that his second “consistently retold the confession of Mr. Mason’s murder as it was told to him by Thompson.”

In a separate criminal case, evidence collected by investigators suggested Thompson was “trying to distance himself” from the area where Mason was found killed, police added.

“It appears in several of the electronic devices” analyzed in the separate case “that a portion of time was deleted from the SMS messages, call log, and timeline from around the time of Mr. Mason’s murder,” the charging documents said.

“Furthermore, a federal investigation was conducted and numerous arrestees were asked if they had any information on the murder of the DC Police Officer, but no one was able to provide a single detail,” wrote police, adding that the private details and electronic evidence “strongly supports Thompson’s confession that he murdered Mr. Mason.”

Thompson is identified in the charging documents as the leader of a drug organization called “The Slickest Ones,” or TSO, with a territory centered around Elgin Avenue.

Lt. Terry McLarney, one of the Baltimore Police investigators behind the investigation, which also involved the FBI and ATF, said at Wednesday’s news conference that the new partnership on cold cases with the Baltimore State’s Attorney’s Office would be “really good.”

“We have the FBI. We have Kurt. Things are getting better,” McLarney said.