WASHINGTON – A construction worker was killed and another was severely injured after being trapped for about four hours under a 50,000-pound piece of concrete following a partial parking garage collapse at the Westfield Montgomery Mall in Bethesda.

Montgomery County Assistant Fire Chief Scott Graham says that the collapse happened at about 1:45 p.m. Thursday in a 40-foot area between the second and third levels of the three-level garage outside the Macy’s entrance to the mall, at the corner of Democracy Boulevard and Westlake Drive.

Paramedics quickly began attending to the second worker and a medical helicopter landed, awaiting the chance to bring him to a hospital. But the parking garage had to be stabilized before getting the second injured man out, and at one point the concrete began to shift. He was freed at about 6 p.m. and put into an ambulance, which brought him to the helicopter.

The parking garage was not open to the public at the time of the incident. Fire officials are describing the incident as a construction accident.

The county police blocked off much of the parking lot, as well as several streets around the mall.

Officials are now investigating the incident.

WTOP’s John Aaron contributed to this report. Follow @WTOP on Twitter.