BOSTON (CBS) — A construction worker died while working on the demolition of the Government Center Parking Garage in Boston Saturday night. Boston Fire Commissioner Jack Dempsey said the worker sustained a “substantial fall” from the ninth floor of the garage doing demolition work, causing a partial collapse of the garage.

“Any building being demolished is a dangerous scene,” Dempsey said. “Probably more dangerous than when they’re putting them up.”

Boston Police Captain Kelley McCormick said the worker was operating a “smaller” worker crane when the floor came crashing down. There was debris laying on top of the equipment after it fell.

Suffolk County District Attorney Kevin Hayden said the worker was a young man, but did not reveal his name. He is a member of the International Union of Operating Engineers Local 4.

Boston firefighters were first called to the area of 1 Congress Street a little past 5:30 p.m. about a report of a partial collapse of the garage.

John Moriarty & Associates released a statement about its job site and the incident, saying a concrete slab on the ninth floor on the east side of the Haymarket Garage collapsed onto the eighth floor.

“Our heartfelt thoughts and condolences go out to the loved ones of the worker who lost his life. JMA remains committed to providing a safe and healthy workplace for all our employees and trade partners,” they wrote.

All the other subcontractors working demolition at the time were evacuated from the building safely.

Crews have been working to deconstruct the empty garage for months.

There was serious traffic disruption in the area for the rest of Saturday night as engineers make sure the area is safe for drivers and MBTA riders using the Orange Line. Streets around Haymarket, including the Sumner Tunnel, were shut down for the night.

“The Orange Line runs right underneath that site,” said McCormick. “So just for safety reason, we want to make sure that site isn’t damaged in the weight of all the collapsing material. So MBTA is currently doing that evaluation with structural engineers, and our engineers will do the building to make sure the building is stable.”

Boston Mayor Michelle Wu spoke alongside city officials on Saturday night, calling the incident a “horrible tragedy.” She said the city is committed to figuring out what happened.

“My heart goes out to the family and loved ones of the worker here tonight,” Wu said. “This is a very complex site, and we know the workers who take on the risks of this…their families should never have to worry about whether they are coming home at night.”

People stopped and stared at the scene throughout Saturday night, trying to comprehend what had happened. Boston EMS says a bystander was taken to the hospital for evaluation but had no physical injuries.

“Absolutely crazy,” said witness Danah Ringel. “I was in my apartment watching TV and heard all the sirens.”

OSHA has taken the scene over for the remainder of Saturday night. The incident is still under investigation.