I-5 Bridge Collapses, 2 Cars Plummet Into Water

massive bridge collapse overnight on that busy stretch of interstate 5 just north of seattle, so many cameras capturing this drama and abc's neal karlinsky is there for us in mt. Vernon right now.... See More

massive bridge collapse overnight on that busy stretch of interstate 5 just north of seattle, so many cameras capturing this drama and abc's neal karlinsky is there for us in mt. Vernon right now. Good morning to you, neal. Reporter: Good morning, josh. This sight is really incredible. A huge section of the bridge just snapped free and dropped straight down into the river. Overnight we spoke with one of the people who was in his car at the time and fell down with it. We have vehicles in the water. Reporter: The chaos began just before 7:00 p.M. As a 150-yard-long chunk of this bridge on i-5, the main freeway on the west coast, suddenly dropped 120 feet into the frigid waters of the skagit river. Two cars and three people plummeting into the waters below. I hit the brakes. The weight of the trail and everything else we went right off the bridge. Reporter: As water began rushing into his cardin says he knew his shoulder was dislocated. Couldn't see my wife in the passenger seat. I asked her if she was okay. She wasn't responding. Popped my shoulder back in so i could unbuckle everything. Reporter: He managed to get his door open and escape with his wife. Soon finding himself talking to another man also sitting on the hood of his car in the water and also remarkably okay. Rescuers rushed in by boat relieved to learn that only three people fell through. All injured but lucky to be alive. It scares me to think it could have been me, that we missed it by a couple minutes. Reporter: Police say it appears an oversized semi truck struck a steel beam above the roadway and that may have triggered the collapse, though the bridge is old, built in 1955 and in need of constant work including two repairs just last year. Authorities and drivers alike know this could have been so much worse. 70,000 vehicles cross this bridge every day. It's just remarkable more cars didn't drop into the river. Investigators will be back out here this morning going over their clues and trying to determine if it was just that oversized truck to blame or something more. Josh? Just a stunning stroke of luck. Thank you, neal karlinsky there.