An Alaska State Troopers helicopter crashed during a rescue mission, killing all three people on board, officials said.Emergency workers reached the wreckage early on Sunday and found the bodies of the pilot, a state trooper and a snowmobiler who had been rescued after becoming stranded near the small town of Talkeetna, Reuters reported.The helicopter had failed to arrive at a rendezvous site to meet medics late on Saturday, Alaska State Troopers said in a statement.