A concrete slab fell from a Washington state overpass killing a young couple and their baby.

The misfortune occurred on State Route 410 Monday morning. The overpass above was in the process of a sidewalk construction project when a large piece of concrete barrier fell below, crushing a moving truck occupied by the victims, according to NBC News.

The victims, a couple in their 20’s and their baby, were driving under the overpass at the time. There were no construction signs on the street and no workers guiding traffic.

“We were just heading down the street…and I could hear three snaps and down it went on top of the truck,” said witness Dawn Nelson, who was riding in a car behind the truck. “There was nothing anyone could do. It was just surreal.”

There had been ongoing construction on SR 410 for the past few weeks. The project was granted to the City of Bonney Lake to add a sidewalk on the road to provide safer travels for pedestrians and bicyclists.

Dan Grigsby, the Bonney Lake Public Works Director, said that the job included taking down part of the existing bridge to make room for the new sidewalk across the old bridge. To help with the work, the city hired a contractor to carry through the plans.

Grigsby also said that in the plan, it stated that if any portion of the Route was going to come down, the contractor was required to shut down the street below, Angeline Road. At the time of the accident, the contractor was working on a small section of the permanent bridge barrier. There was nothing scheduled for Monday to come down on the road below.

“They had been flagging traffic for the last couple of days when they were working on that … makes it even more sad I guess that they weren’t doing that today,” said Dave Berg, a resident who lives a couple hundred feet down the road. “It just sounded like thunder. I didn’t think much of it when I was in the house… It’s disturbing when it’s that close to home.”

Angeline Road is now closed to traffic while the construction crews continue to clear the debris from the road. Authorities reported that they are conducting their investigation.