http://www.chron.com/news/article/Passers-by-rescue-children-from-icy-Utah-river-2436555.phpSays he put his handgun gun against the window underwater and fired:
Willden said he tried unsuccessfully to open windows and doors. He then used his firearm just as he had done in training for his current job as a bodyguard and Department of Defense contractor.
One thing that's not clear to me is how the driver ended up outside the vehicle with all the windows and doors closed.