Three killed after firefighting helicopters collide while battling blaze in California

Two helicopters collided mid-air while fighting a wildfire in Riverside County, California, resulting in three fatalities.
The victims were a Cal Fire division chief, a Cal Fire captain, and a contracted pilot assisting firefighting efforts.
One helicopter was able to land safely after the collision while the other crashed into a hillside.
The incident occurred as the helicopters were responding to a vegetation fire that had spread from a structure fire.
The National Transportation Safety Board is investigating the cause of the mid-air collision.