A woman has been arrested after allegedly driving a car into a Los Angeles bus, killing two people and injuring six others.
Hours later, a news helicopter crash covering the incident crashed nearby, killing the TV reporter and pilot who were onboard.
The US National Transportation Safety Board said it was investigating the circumstances of both crashes.
Bailee Lynn Rios, 36, of Simi Valley, was arrested on Tuesday night, local time, and was being held at a Los Angeles jail with bail set at $US4 million, police said on Wednesday.
The helicopter crashed about two hours after police say Ms Rios drove her 2004 Ford Expedition the wrong way down a busy avenue, ran a red light and struck a vehicle before hitting the bus.
One passenger was ejected from the bus and another was partially ejected, police said.
Ms Rios's mother, Cindy Rios, said she was shocked and saddened by the string of events.
The two people who died in the bus crash were identified as Daniel Castillo, 46, of Los Angeles, and Gage Weida, 31.
Aerial reporter Eliana Moreno and experienced pilot George Marciniw were killed while flying over the fatal bus crash, when their helicopter fell from the sky in the neighbourhood of Chatsworth, in the San Fernando Valley.
"That video is probably the most important evidence that we have discovered so far," National Transportation Safety Board investigator Fabian Salazar said on Wednesday at a news briefing.
The NTSB said it was also investigating the bus collision.