D.C. police arrested two men Thursday in separate fatal shootings, alleging that one of them opened fire at people on a street corner because he was mad about the theft of his favorite pistol, and that the other suspect used a handgun during a drunken dispute among apartment residents after a Memorial Day weekend cookout.

In each case, the person killed was not an intended target of the attack, police said.

The first shooting, Jan. 17, occurred shortly after 11 a.m. at 16th and U streets SE. The suspect, Torey G. Stockton, 21, of District Heights, Md., allegedly opened fire with a 9mm automatic weapon at several people standing outside King Convenience Store.

In an affidavit filed in D.C. Superior Court, a homicide detective wrote that Stockton was angry about the theft of his gold-plated Glock pistol, which he called “Glizzy.” He fired at least 15 shots from a moving car on 16th Street because he saw acquaintances of the suspected thief, the affidavit says.

Police said Stockton, who is being held without bail on a first-degree murder charge, wounded four victims, including Jasmine Lashai Light, 23, of Southwest Washington, who died at a hospital. Light was not one of the people Stockton was intending to shoot, according to D.C. Police Chief Peter Newsham.

“This was a young lady who, by all accounts, had turned her life around” after troubled teenage years, Newsham said Friday in announcing the arrests.

On the morning of the shooting at 16th and U, Newsham and Mayor Muriel E. Bowser (D) were holding an outdoor news conference a few blocks away, talking about the shooting death of a 14-year-old in the same neighborhood a few days earlier.

The sounds of a new homicide — the gunshots outside the store, followed by wailing police sirens — interrupted the chief as he was lamenting the previous killing.

Speaking to reporters Friday, Newsham recalled viewing surveillance footage of bodies falling outside the store. “I can tell you as a police officer, the video in this case is something that will stay with me for the rest of my life,” he said.

The police affidavit says Stockton posted photos of “Glizzy” on Instagram before the shooting and threatened to wreak violence if the Glock wasn’t returned. He went looking for the suspected gun thief, a former friend, in the vicinity of 16th and U, the affidavit said. When he couldn’t find the man, he allegedly vented his anger on people he knew were “associates” of the ex-friend.

Afterward, Stockton boasted about the shooting on Instagram, according to the affidavit, which says that investigators were able to retrieve incriminating posts that had been deleted.

In the other case, shots were fired about 1:50 a.m. on the Saturday before Memorial Day during a post-cookout dispute involving intoxicated men in the 2200 block of Savannah Terrace SE, police said. The victim, Alexander Mosby, 39, described by Newsham as “a beloved businessman,” was a lifelong resident of the neighborhood and the former owner of District Culture, a now-defunct clothing store in Southeast.

Mosby wasn’t the shooter’s intended victim, Newsham said. The suspect, Tywan S. Porter, 25, of Southeast, was jailed without bond and charged with second-degree murder.

As police questioned witnesses at the scene, a person identified in a police affidavit as Witness 2 recalled having a conversation with another person in the neighborhood shortly after the shooting.

“You know who done it?” the other person said, according to Witness 2.

“Who?” asked Witness 2.

“Fat boy that drives the gray Infiniti.”

Witness 2 reported that “fat boy” had a bad reputation in the neighborhood. The affidavit says Witness 2 gave detectives the plate number of the car that “fat boy” drove. The witness, who couldn’t identify the suspect by name, had written down the number months earlier “in case something happened,” the affidavit says.

Police traced the plate number to Porter, who stands 5-foot-11 and weighs 290 pounds, and they searched his 2008 Infiniti FX3, according to the affidavit.

In the car were three spent 9mm shells, the affidavit says. It says that based on microscopic scratches on the shells, experts determined that the three had come from the same gun that ejected six shells at the crime scene.