UPDATE, 9:18 p.m.: According to the CHP, one victim has been identified as Patrick Ramirez, 45, of San Dimas. The deceased, a 25-year-old male, has not been identified, pending notification of next of kin.
According to a CHP press release, the unidentified rider was operating a 2000 Kawasaki ZR-7, Ramirez a 2000 Yamaha R6.
The unidentified rider was traveling westbound at an unknown speed while Ramirez was traveling eastbound at 40 miles per hour when, for reasons unknown, the unidentified rider lost control of their motorcycle, was ejected and struck the second motorcycle.
Ramirez was thrown from his motorcycle and collided with the road, sustaining moderate injuries.
Alcohol is not believed to be a factor in the crash.
Previously: One person was injured and one was killed in a motorcycle crash on Angeles Crest Highway Sunday afternoon.
The crash was reported around 1:40 p.m. near mile marker 63.50, according to Tatiana Sauquillo of the California Highway Patrol. What communities reside south of the crash were not disclosed, but scanner reports from Los Angeles County Fire divulged the crash happened before a series of tunnels, which would place the incident possibly above the communities of Azusa and Glendora, before Highway 39.
About five minutes after the call came in, Montrose Search and Rescue team members arrived, Sheriff's Reserve Chief Mike Leum told Patch.
Leum and his SAR partner were the first at the scene, along with Sheriff's Air 5.
One victim was administered CPR and pronounced dead at the scene. Another was transported to Huntington Memorial Hospital, Leum said.
At 2:38 p.m., CHP issue a Sig Alert for an unknown duration and eastbound and westbound traffic was being turned around.
How many other people may be involved, as well as the circumstances of the crash remain unknown at this time.
Check back with Patch for updates as we get them.
Note: A previous version of this article stated that Los Angeles County Fire arrived at the scene, however rescue crews stated this is incorrect. Patch regrets this error.