This is being reported on NBC:
The FBI and state police staked out a spot along the route to John Day to stop the caravan. At first, both vehicles complied with an order to pull over, but then the lead vehicle took off, the law enforcement official said.
It didn’t get very far, hitting a snow bank. Finicum, the official said, jumped out of that vehicle “brandishing a firearm.” He was shot and killed.
This account of things appears to be corroborated by a guy claiming to have been driving one of the two vehicles involved. A teenage girl who was with the Bundy crew claimed that Finicum had his hands up when he was shot, but she also said she was hiding on the floorboards of the truck when this happened.
See also Charles Pierce, in posts written before and after the arrests.
Also, too: Eyewitnesses knock down conspiracy theories about LaVoy Finicum dying on his knees