LOS ANGELES (CBS) — A 16-year-old boy was arrested on suspicion of shooting and killing another 16-year-old in downtown Los Angeles Tuesday.

The shooting occurred about 3 p.m. on Third Street, just west of Hill Street, police said.

A police officer who was nearby witnessed what happened and took the suspect into custody without incident, LAPD Detective Gus Villanueva said.

A motive for the shooting was unclear, Villanueva said.

The victim died at a hospital, LAPD Officer Karen Rayner said.

The suspect's name was not released because he is a juvenile. Police also withheld the victim's name.

(©2011 CBS Local Media, a division of CBS Radio Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. Wire services contributed to this report.)