Collapsed crane deadly in downtown Seattle four people were killed

Collapsed crane deadly in downtown Seattle four people were killed.Why did the crane collapse in Seattle?
Why did the crane collapse in Seattle?
Why did the crane collapse in Seattle?

 The new video shows the moment a crane collapsed in South Lake Union Saturday afternoon.  Four people were killed when part of the crane from the construction site in the future fell into traffic below.

 Scott Gaines is on his way to work, the dashcam in his car has collapsed.

 Seattle Fire Department said a woman and three men had died before the first firefighters arrived on the scene.  Seattle Public University confirmed that freshman Sarah Wong is one of the victims.
The emergency rescue team reacted to the spectacle at Mercer Street and Fairview Avenue in South Lake Union neighborhood at about 3:30 pm  "It was a terrible day in Seattle when something like this happened in our city center," said Mayor Jenny Durkan.  "Most people drove down this road at some point in their lives. But it was time we came together because Seattle was a city gathered together."

 Some people told KING 5 that they witnessed the crew working to dismantle the crane earlier in the day.  Washington State Department of Labor and Industry is leading an investigation into the cause of the crane collapse.
 Tim Church, spokesman for Labor and Industry, confirmed the investigation of four companies: GLY Construction, a subcontractor of Northwest Tower Crane Company and Omega Morgan, and Morrow Equipment Company.  Half of the cranes in Washington state are in Seattle.    Source: ThisIsButter.