A tractor-trailer driver was killed in a fiery crash that closed the Woodrow Wilson Bridge and trapped three workers underneath the bridge Wednesday morning.

The Wilson Bridge — and thus a section of the vital Capital Beltway — was completely closed in the aftermath of the crash.

An empty tractor-trailer traveling east on the express lanes of the Outer Loop of the Beltway lost control just before 11 a.m. and crashed into highway construction vehicles parked along the bridge, according to Maryland State Police.

A bridge maintenance crew was examining the bridge using a boom truck, with three workers under the bridge in a work bucket and one worker in the truck. A warning truck was behind the boom truck to protect its crew from just such a crash.

The tractor-trailer hit the warning truck, pushing it into the boom truck. The tractor-trailer and the boom truck immediately caught fire. A second fire started when another worker's truck parked near the scene of the crash ignited.

Photos from the scene show the cab of the tractor-trailer completely engulfed in flames. Witnesses likened it to a bombing.

"At first I thought, actually, I thought there might have been a breach with Homeland Security and somebody was going to bomb the bridge or something, because the black smoke was just so high up in the air," one woman said.

Drivers described a scary experience.

U/D #WWB Appears incident started with multi-vehicle collision on bridge involving boom truck - resulting in fire. 3 workers were stranded in extended bucket under bridge. Preliminary report - injuries and 1 fatality from crash 3 workers rescued and boom truck operator is OK. — Mark Brady (@PGFDPIO) June 20, 2018

DC area friends - avoid the Wilson Bridge pic.twitter.com/yeyZtVyWUC — Coach Gator (@TheCoachGator) June 20, 2018

"There's helicopters everywhere," a man said. "There's more emergency vehicles than you'd like to see on a bridge. So we were worried about a lot of things. Just thankful we got off there."

The tractor-trailer driver was kiiled, fire officials say. Authorities are working with the trucking company and the medical examiner to identify the deceased.

Beneath the flaming boom truck, the three men in the bucket used safety roped to lower themselves down to a police boats that raced to the scene.

"The unusual part of this was because we had three workers in a boom, aerial boom over a bridge working over the Potomac River," said Greg Shipley of Maryland State Police. "It could have been a lot worse; we're glad it wasn't."

The workers who were rescued and the driver of the boom truck were taken to a hospital and are expected to survive. They later returned to the scene to meet with accident reconstruction investigators.

Four other people on the bridge were taken to the hospital for treatment.

During the chaos on the bridge, fuel spilled into the Potomac River below. Hazmat crews are on the scene to clean it up.

All lanes of the Wilson Bridge reopened nearly 12 hours after the crash.

The Wilson Bridge connects Alexandria, Virginia, to Fort Washington, Maryland.