"It was a floor upon floor, collapsing all the way down to the ground floor," Miami-Dade Fire Rescue Capt. Louie Fernandez said.
The trapped worker was pinned inside a vehicle. He was receiving oxygen, had an IV inserted into him and was being treated by a physician and a paramedic. Officials did not describe the extent of his injuries. They said it could be hours — possibly even days — before they can rescue him.
"It's going to be a long, tedious effort," Fernandez said.
Dogs, firefighters and other people in hard hats walked over piles of concrete, plywood and metal to look for other possible victims. Authorities believed at least one more worker was still unaccounted for, and they were trying to make sure everyone else was OK. Many workers left the site without telling authorities.
Victoria Buczynski of Miami said she saw the collapse while she was working at Gurkha Cigars across the street from the construction site at the Miami-Dade College.
"It fell to the ground like a house of cards," Buczynski said. "The construction workers started running out, screaming. It was loud. Our entire building shook."
No students were in the area at the time. They campus was evacuated and closed for the rest of the week. Investigators planned to pick through the rubble to see what caused the garage to crumble.
"We just know that the roof collapsed," Miami-Dade Fire-Rescue spokeswoman Griselle Marino said.
William P. Byrne, president and chief executive officer of the garage contractor, Ajax Building Corp., said an internal review was being launched to determine the cause. Byrne said the company would embrace "any additional protocols, policies and procedures that will enhance and ensure the continued priority of safety."
Marino said three people were initially trapped in the rubble, including the man who died. Another eight were taken to a hospital, she said. Two injured workers were treated on the scene.
One of the rescued was pulled out from under a steal beam by four firefighters. His face and hands were bloody and he was put on a stretcher and carried away, according to a video shot by Miami-Dade Fire-Rescue and provided to The Associated Press.
The construction site looked like a typical one. A large crane stood beside the pile of rubble. Pickup trucks, trash bins and a tractor-trailer were nearby, as were ladders, a cooler and piles of wood.
Ground was broken on the $22.5 million project in February, and the 1,855-space garage was to be finished in December, according Ajax's website.
The first floor was to have classroom and office space. The structure is next to the college's main office building and nestled among other campus buildings.
The college serves about 8,000 students and is one of several campuses in the Miami-Dade College system. This campus opened in 2006.
The identity of the worker who died was not immediately released.