Pedro Santiago Mateos, 35, of Humboldt Park, has been identified by the Cook County Medical Examiner. His death has been ruled an accident, the ME said.
Authorities began responding to the scene in the 700-block of East Oakwood Boulevard around 11 a.m. Thursday.
Chopper 7HD flew above the scene, with more than a dozen firefighters on the scene as a section of a building collapsed in. Firefighters could be seen digging through the rubble
"Suddenly there was a loud boom and I felt the floor shake," said neighbor Elizabeth Kertowidjojo.
For a moment neighbors wondered if the collapse was supposed to happen, as part of the project.
"But then I saw them yelling and they were trying to dig something out, so I knew something bad had happened," she said.
CFD said a construction worker became trapped under three to five feet of debris. Firefighters on the scene were able to free the worker, who was taken to an ambulance.
WATCH | CFD gives update on building collapse
CFD gives update on building collapse
CFD said the worker was transported to University of Chicago Medical Center in grave condition. The Cook County Medical Examiner later said they had been notified of his death.
It took firefighters 45 minutes of digging by hand to free the worker.
"We had approximately 10 members working in the hot zone at a time," said CFD Deputy District Chief Shaun Hayes. "We would let them work for a little while, then we would rotate them out."
The collapse occurred in a three-story, vacant building that was currently under construction. Two other workers were at the site at the time of the collapse and were not trapped, CFD said.
Officials with the city's Buildings Department are still trying to determine what triggered the partial collapse. The department said the building is 141 years old. Crews worked to secure the damaged property before demolishing what was left.
"It is two connected townhomes," said 4th Ward Alderman Sophia King. "They probably will not have to demo the other half where a family lives currently, but they will be displaced for some time."
Neighbors said the vacant townhouse had been under construction for months.
"It wasn't really done in a way we were comfortable with," Kertowidjojo said.
The city said a permit for Interior Demolition Only was issued by the Department of Buildings in September 2022, and the work that was in progress was not in compliance with approved plans for demolition.
RELATED: City investigating Chicago building collapse; site only permitted for interior renovation: officials
The city also said those who violated health and safety codes will be held accountable.
The ABC7 I-Team obtained documents naming Luka Chirayil as the current owner. ABC7 attempted to call him Friday, but he said he has no comment at this time.
The Department of Buildings said, in part they take "public safety and quality of life issues very seriously. Our thoughts and prayers are with the workers impacted."