April 2012: LAPD shoot 90 bullets at unarmed teenager after high speed chase, killing him

[IcyPeas]

5. they thought he was armed:

also from the linked article:

During the chase, Arian called 911, and according to a partial transcript of the call released by the LAPD, he claimed to have a gun and made threats to the police.

"I have been arrested before for possession of destructive devices, I'm not afraid of the cops," he told the dispatcher. "If they pull their guns, I'm going to have to pull my gun out on them."

The dispatcher, according to the release, pleaded for Arian to surrender, saying "I don't want you to hurt yourself."

Arian responded with expletives and warned that the police are "going to get hurt."

Police did not recover a gun from the scene.

After cutting across lanes, Arian stopped, jumped out of his car and began running on the freeway. Facing police while back-stepping, he extended both arms with clasped hands, a gesture captured on video by a KTLA-TV news helicopter.

But as Arian headed toward the shoulder of the freeway in the vicinity of a vehicle that had pulled over, he turned again and assumed what police called a "shooting stance." He appeared to wield a weapon. His uncle believed it was a cellphone. Sources familiar with the investigation who were not authorized to speak publicly confirmed that it was a cellphone.

sounds like suicide by cop to me.