Attorneys for the men did not immediately respond to requests for comment.

At the time of the shooting, Thompkins was under the supervision of the federal Court Services and Offender Supervision Agency, police said in the affidavit, after pleading guilty in 2019 to an illegal gun-possession charge. At the time, he was sentenced to 36 months in prison with one year of supervised release.

Martin and the Morgan brothers were killed on the deadliest week of this year, when 16 people were killed in the first six days of August. Their deaths marked a turning point in the District, when public officials were forced to contend that people in D.C. were being killed at a pace not seen since the 1990s.

As of Tuesday, with 253 homicides, the city is on track to record more killings this year than in any year since 1997. Top officials have declared public safety a crisis in the nation’s capital.

The Tuesday arrests and their accompanying affidavits provide no clarity about the motive behind the triple killing. In the documents, however, police said the three victims and two suspects interacted in a nearby park shortly before the shooting. In that interaction, police said Thompkins was “seen reaching his right hand into the front of his waistband in the motion of drawing and brandishing a firearm.”

The three victims walked away from the park. Police said one of the deceased men was captured on video walking backward “while holding a handgun.”

After they left, police said Bryant and Thompkins followed them and began shooting. James Morgan was found with nine gunshot wounds, Jamal Morgan with four and Martin with two, according to the affidavit.

“The suspects consciously decided to conspire, pursue, track behind and entrap the decedents by going around the block to flank them,” police wrote in charging documents.

Police said two firearms were recovered near the deceased men. They also said that Bryant and Thompkins were affiliated with a known neighborhood crew in Adams Morgan.

Asked at a news conference Wednesday evening what led to the shooting, D.C. Police Inspector Kevin Kentish said, “At this point, we don’t know. ... However, I can say with certainty there was some sort of altercation that happened prior to the homicide.”

Authorities said they arrested Bryant and Thompkins inside a townhouse in Prince George’s County, Md. They found three rifles and two handguns in Thompkins’s room, police said, and an additional firearm under the sink cabinet of a bathroom on his floor.

Bryant declined to answer questions from the police, according to the affidavit. Thompkins said he had “known Bryant for his entire life,” and then refused to answer further, police said.

Also Tuesday, police arrested and charged a man in a 2021 killing. Juan Manuel Guerra, 31, of Southwest Washington, was charged with second-degree murder in the killing of 31-year-old Peter Miller III.

Miller was attacked Oct. 6, 2021, in the 900 block of Maine Avenue SW, and was pronounced dead five days later.

In charging documents, police said Guerra, Miller and others had been gambling inside an apartment before the incident.

An attorney for Guerra was not listed in court records. Efforts to reach his relatives were not successful.