The teenager fatally shot by police in South L.A. over the weekend left a farewell note to his family before the encounter and appears to have wanted to end his life, Los Angeles Police Chief Charlie Beck said Thursday.

The move underscored the challenge law enforcement agencies confront in trying to keep video of police shootings confidential during a time of heightened public scrutiny of how officers use force, particularly against African-Americans. Snell jumped out and ran, and a chase followed, police said.

"The quick release of the Snell slaying videotape within days after the shooting is the best argument against LAPD officials' contention that tapes can't be released immediately", Hutchinson said.

Beck said body-camera video from the encounter matched the officers' narratives and that he does not intend to release the footage.

The gun turned out to be a replica gun with an orange tip that had been painted black.

The officers who shot him - who claimed Snell posed a threat and turned toward them still holding the weapon - "The recent release of the security video leading up to the fatal shooting of Carnell Snell is not conclusive of whether the shooting is justified", the letter reads.

Amid rising concern over police-involved deaths, two black men in their 30s were killed earlier last week in Southern California: Reginald Thomas, who died after being hit by a police Taser in Pasadena, and Alfred Olango, shot by San Diego police while holding an electronic cigarette that police mistook for a weapon.

"Body camera footage or other video doesn't provide transparency if the public never gets to see it".

Start Time, Streaming Video For Tuesday's VP Debate
But interest in what is taking place - even for the presidential debate - doesn't necessarily matter when people vote. The vice-presidential debate will last approximately 90 minutes and will be divided into nine 10-minute segments.

Some residents questioned the police account, including whether Snell had a gun.

Snell was shot after officers tried to pull over a auto he was in because it had paper license plates that didn't match the year of the vehicle.

Beck said the video showed Snell had an opportunity to get rid of the gun but chose to keep it when he ran around a corner of the strip mall, disappearing from the footage that showed two officers running after him. All then disappear from view because they were no longer within the range of the surveillance camera.

Regardless of whether the footage supports what police say, Hutchinson said, videos "must be released promptly to assure transparency and restore public trust in the impartiality and integrity of investigations".

The caller reported a man with a gun matching Perez's description, Beck said.

Beck has said that the video clearly refutes reports that some of the shots were fired when the man was on the ground. "People shouldn't feel like when the police come to your house that what's happened to you is going to be splashed all over the Internet". The call was placed about 20 minutes before the shooting.

Both shootings generated protests in Los Angeles.