"It's not something you see every day," said Jimmy O'Connor, the owner of two local pizza restaurants who was driving on another bridge parallel to the one that collapsed. "People were starting to crawl out of their cars."
He said he and his girlfriend were about 400 yards away on the Burlington Bridge when they heard "just a loud bang."
"Then we looked over and saw the bridge was down in the water," he said.
He pulled over and saw three vehicles in the water, including the camping trailer that landed upside-down, he said.
The bridge was not classified as structurally deficient, but a Federal Highway Administration database listed it as being "functionally obsolete" — a category meaning that the design is outdated, such as having narrow shoulders and low clearance underneath.
The bridge was built in 1955 and has a sufficiency rating of 57.4 out of 100, according to federal records. That is well below the statewide average rating of 80, according to an Associated Press analysis of federal data, but 759 bridges in the state have a lower sufficiency score.
According to a 2012 Skagit County Public Works Department report, 42 of the county's 108 bridges are 50 years or older. The document says eight of the bridges are more than 70 years old and two are over 80.
Washington state was given a C in the American Society of Civil Engineers' 2013 infrastructure report card and a C- when it came to the state's bridges. The group said more than a quarter of Washington's 7,840 bridges are considered structurally deficient or functionally obsolete.
Democratic Rep. Judy Clibborn, who leads the transportation committee in the state House, said the bridge wasn't one that has been a focus for lawmakers.
"It is shocking that I-5 would have something happen like this," she said.
Clibborn said the collapse will call attention to the issues facing bridges — especially the old bridge over the Columbia River that connects Vancouver and Portland, Ore.
Sligh said his wife was "doing OK" and that he had "lots of cuts."
"You're kind of pinching yourself and realize you're lucky to be alive."