LOS ANGELES (AP) — Police arrested a man on suspicion of murder after his brother was fatally shot during a weekend family birthday celebration in South Los Angeles.

Los Angeles police Lt. Jeff Nolte said 40-year-old Louis Hill was arrested Sunday after being interviewed by investigators.

Louis Hill is suspected of fatally shooting his 48-year-old brother Derrick Hill on Saturday shortly before 9 p.m. on the 800 block of E. 78th Street, Nolte said.

Mother Doris Hill said the family was celebrating her granddaughter’s ninth birthday with ice cream and cake when Louis ran in and said he’d been jumped on the corner.

His big brother Derrick went out to see what happened and the family next heard a gunshot. Their mother said someone else shot Derrick once in the head.

Doris Hill said neighbors told police that it was her son Louis Hill who shot his brother, but that she didn’t believe it. She said she went into the police station Sunday to talk to officers.

Derrick lived with his mother at the address and knew everyone in the area, Doris Hill said, which is why he went out to check on things.

“He was a nice person, he was a people person, he was a mama’s boy,” Doris Hill said.

Nolte said investigators didn’t believe gang-related activity is involved. Many details of the case were withheld because of the pending investigation.

But Nolte said detectives felt they had sufficient evidence from their preliminary investigation to arrest Louis Hill on suspicion of murder.