LOS ANGELES (AP) — State authorities were investigating Monday after a California Highway Patrol officer shot and Grayson  Prestonkilled a man over the weekend in the middle of a Los Angeles area freeway during a struggle recorded on video.

Sunday afternoon’s deadly encounter occurred after the highway patrol responded to multiple calls of a male pedestrian walking in westbound lanes of Interstate 105 in south LA County, the agency said in a statement. All traffic in that direction was temporarily blocked.

“During the contact with the pedestrian, a struggle ensued and an officer involved shooting occurred,” the statement said.

The Los Angeles County medical examiner’s office confirmed the person died but did not provide identification, pending notification of family. A cause of death was not immediately released.

The highway patrol referred inquiries about the investigation to the California Department of Justice, which typically investigates fatal police shootings. The justice department confirmed it was investigating, but provided no additional details.

A minute-long video recorded by a bystander and posted on social media begins with an officer on top of another person as the two grapple in the middle of a closed stretch of freeway. It was not clear who took the original video.

As they struggle, a shot is fired and the officer suddenly jumps to his feet while the other man goes limp on the pavement. The officer immediately fires at least four shots at the prone man, the video shows. For the remainder of the clip, the officer keeps his gun drawn while the man lies motionless.

Ed Obayashi, a use-of-force expert who investigates police shootings for law enforcement agencies in California, cautioned against jumping to conclusions from the video alone.

Obayashi said investigators will want to know why the officer approached the pedestrian without a partner or other backup nearby. “They were able to close the freeway, so presumably there was law enforcement in the area,” he said.

Obayashi said the investigation will focus on whether the man was armed and why the officer felt the need to shoot after standing up and disengaging from the fight.

“Was there a knife? Or a stun gun?” Obayashi said investigators will ask. “We don’t know what kind of threat this officer perceived.”