The incident happened just before 5 p.m. in the 10000 block of Obregon Street in an unincorporated section of Whittier.
The department says deputies were on patrol when they stopped to speak to a man who was walking in the middle of the street. As they spoke to him from his vehicle, they say he pulled out a firearm. That's when he was shot.
The Los Angeles County Sheriff's Department says the man died at the scene. His age and identification were not immediately released.
A gun was recovered.
No deputies were injured.