Don Cornelius -- 911 Call Made By His Son

We now know who made the call to 911 after Don Cornelius shot himself in the head early this morning -- it was his own son.

Law enforcement sources tell TMZ ... one of Don's two sons made the call around 4:00 AM ... and paramedics were immediately dispatched to Don's Sherman Oaks home in an effort to save his life.

Don was transported to a nearby hospital -- where he was later pronounced dead.