One person was killed and two workers who were unaccounted for following the partial collapse of a parking garage in Philadelphia are now presumed dead, Mayor Cherelle Parker announced Thursday night.

A garage under construction for Children's Hospital of Philadelphia employee parking partially collapsed along Grays Ferry Avenue.

"The floors was like going like one by one as it was like collapsing. And then there was a guy that was trapped underneath," Kurtis Carter, who witnessed the incident, told 6ABC.