Yesterday all of the following happened;

Palmdale - A teen male was arrested for deliberately setting fire to a home that killed four people inside - it appears to have been a wanton act of mass-murder, not just arson.

Downtown L.A. - Some bicyclists in a large group traversing Exposition Boulevard near USC campus got into a road-rage incident. The vehicle followed a few of the group into a big empty parking lot near BMO stadium. The vehicle accelerated rapidly toward them hitting / killing a 16 year-old, then drove away. Witnesses told cops that the other cyclists close to the incident fled without waiting for ambulance or law enforcement. 

Sylmar - Highway Patrol got a call about a vehicle stopped on the shoulder of a highway transition-road bridge. Responding officer pulled up behind vehicle - without warning, person bolted from inside - jumped over the railing, falling 100 feet to his death.*

- Downtown L.A. - a driver appears to have intentionally rammed his SUV through railroad crossing barriers into the side of a passing train.