Part of a construction crane which fell onto cars on Mercer Street, killing people and injuring others, is seen hanging off of a Google office building in Seattle, Washington, U.S. April 27, 2019.

Construction workers gather together on the sidewalk near a construction crane which fell onto cars on Mercer Street, killing people and injuring others, in Seattle, Washington, U.S. April 27, 2019.

Seattle emergency personnel inspect the scene where part of a construction crane fell in a deadly accident on Mercer Street in Seattle, Washington, U.S. April 27, 2019.

Part of a construction crane that fell in a deadly accident is removed from the scene on Mercer Street in Seattle, Washington, U.S. April 27, 2019.

Part of a construction crane which fell rests on a partially crushed car on Mercer Street in Seattle, Washington, U.S. April 27, 2019.

Seattle emergency personnel view part of a construction crane which fell onto cars on Mercer Street, killing people and injuring others, in Seattle, Washington, U.S. April 27, 2019.

Blake Haner looks on at the scene as he holds flowers for the victims after a construction crane fell in a deadly accident on Mercer Street in Seattle, Washington, U.S. April 27, 2019.

The back side of a construction crane which partially fell onto cars on Mercer Street, as seen from Valley Street, killing people and injuring others, in Seattle, Washington, U.S. April 27, 2019.

A member of the Seattle police department inspects one of the cars crushed by part of a construction crane on Mercer Street, which killed four people and injured several others in Seattle, Washington, U.S. April 27, 2019.

Workers stand by at the scene where part of a construction crane fell in a deadly accident on Mercer Street in Seattle, Washington, U.S. April 27, 2019.

Construction workers talk with each other on the sidewalk after a construction crane fell onto cars on Mercer Street, killing people and injuring others in Seattle, Washington, U.S. April 27, 2019.

A view of part of a construction crane which fell onto cars on Mercer Street, killing people and injuring others, in Seattle, Washington, U.S. April 27, 2019.

A member of the Seattle police department inspects one of the cars crushed by part of a construction crane on Mercer Street, which killed four people and injured several others in Seattle, Washington, U.S. April 27, 2019.

Damage after a construction crane collapsed is seen on the roof of a building in Seattle, Washington, U.S. April 27, 2019, in this picture obtained from social media. CHAD TILLEKERATNE/via REUTERS

Seattle emergency personnel are reflected in the Google office building that part of a construction crane fell from, on Mercer Street in Seattle, Washington, U.S. April 27, 2019.

Seattle Mayor Jenny Durkan, left, looks on as Seattle Police Assistant Chief Eric Greening speaks near the scene where part of a construction crane fell in a deadly accident on Mercer Street in Seattle, Washington, U.S. April 27, 2019. Image used for illustrative purpose.