LAPD sergeant, civilian killed in freeway crash near Getty Center

Two people, including a sergeant with the Los Angeles Police Department, were killed Monday morning following a multi-vehicle crash on the 405 Freeway near the Getty Center.
A third person was injured in the collision.
What we know:
Officials said it all began when the LAPD sergeant stopped on the southbound lanes of the freeway at Sunset Boulevard in Brentwood to help other people involved in a separate crash around 2:30 a.m.
While at the scene, another driver slammed into the LAPD unit where the sergeant was standing and struck him.
The sergeant was rushed to Ronald Reagan UCLA Medical Center in grave condition. He was later declared dead by medical personnel.
A SigAlert was issued near the Getty Center and was expected to be in place for hours.
What we don't know:
The names of the crash victims have not been released.
The Source: Information from the Los Angeles Police Department.