This from reporter Jen McLain in the field and Tania Chatila in the newsroom:

The Los Angeles County Sheriff’s Department has placed Rosemead High School on lockdown and blocked off part of Rosemead Boulevard as they search for a man with a gun, officials said.
The unidentified man was first seen in an area neighborhood at 10:30 a.m., authorities said.
Officials at nearby Rosemead High were not available for comment, but did confirm the campus was on lockdown.
Rosemead Boulevard between Mission Drive and Lower Azusa Road has been blocked off to traffic.
The suspect is described as a light-skinned Hispanic male, wearing shorts. He was last seen jumping over a fence at the corner of Rosemead Boulevard and Mission Drive, police said.