LOS ANGELES — A teenage girl was shot and killed in her Southern California home, and deputies are searching for her 18-year-old brother, who they say is a suspect, authorities said.

Eddie Alvirez is believed to have run off with the handgun after the incident occurred around 5:45 p.m. in the desert city of Lancaster, the Los Angeles County Sheriff’s Department said in a news release Wednesday. Officials confirmed the 13-year-old victim was rushed to a local hospital, where she died. KCBS-TV reports her name was Marlena.

“My heart hurts she just started school. She loved going to the movies,” a relative wrote to The Associated Press.

Deputies say Alvirez shared a bedroom with the victim and another sister and that upon arrival, discovered that Alvirez had been in possession of a handgun. It is not yet clear what led up to the shooting, but family members say they believe he may have panicked after firing the gun.

“I know my nephew, I believe it was an accident. He didn’t intentionally hurt her. He’s loved his sisters from when they were babies,” family member Vanessa Zamora told KCBS-TV.

Alvirez was last seen wearing a white T-shirt, gray or black shorts and Air Jordan sneakers.

“We just hope Eddie doesn’t hurt anybody else or hurt himself,” Sgt. Richard Biddle told the Los Angeles Times. “We’re hopeful he will come and talk to us, or let us come and talk to him, or go to a sheriff’s station. His family has suffered enough tragedy.”