Authorities say a Baton Rouge man shot his teenage girlfriend, her mother, a friend and then turned the gun on himself early Sunday, leaving three people dead, including himself, and one seriously injured — all while a 1-year-old baby was in the apartment.

The murder-suicide took place about 1:20 a.m. Sunday at an apartment complex at 1077 N. Donmoor Ave., and stemmed from a family argument, said Cpl. L’Jean McKneely Jr., a Baton Rouge Police Department spokesman, but he did not say what the argument was about.

Marquiles Whaley, 20, lived at the Donmoor apartment with his girlfriend, Makayla Jones, 18. The couple, along with Jones’ 36-year-old mother, Romander Jones, were arguing when a friend, 38-year-old Shawyn Lollis, went to the apartment to see what was going on, according to Lollis’ sister, Leteisha Perkins.

Shortly after Lollis went into the apartment, Whaley pulled out a gun and shot his girlfriend, her mother and Lollis and then turned the gun on himself.

Lollis, Makayla Jones and Whaley were killed. Romander Jones was wounded and is in a hospital awaiting surgery, said her mother, Mary Wright.

Makayla Jones’ 1-year-old daughter was at the apartment when the shooting took place but was unharmed, Wright said. She said she had been taking care of the baby since the shooting, and she and the baby are staying with her daughter in the hospital.

Two of Shawyn Lollis’ sisters, Leteisha Perkins, 29, and Renitria Holmes, 35, picked up some of his belongings Sunday afternoon from the complex where neighbors met them with hugs and tears. People streamed in and out of a corner store next to the complex, stopping in the parking lot where the sisters stood crying to offer their sympathy.

Perkins said her brother was just in the wrong place at the wrong time when he went to check on Jones after hearing the argument.

Devontra Lollis said Shawyn Lollis, of 1084 Monet Drive, was a “helper” around the Donmoor neighborhood. Perkins said he had “lived place to place,” including on Donmoor Avenue, and he sometimes worked at the nearby corner store.

Holmes said people often described her older brother as a “cool dude.”

“I was working and my brother still comes, ‘Little sister, you need some money? … I’m going to give it to you anyway,’ ” Holmes said. “ … He was just that good to me.”

“This is senseless,” she said. “He didn’t bother nobody, so why? Why my brother?”

Editor’s note: This story was changed July 13, 2015, to delete comments made by Devontra Lollis, who claimed he was Marquiles Whaley’s brother during an interview Sunday. A family member of Whaley’s told The Advocate Monday that Lollis is not Whaley’s brother.