It's too early for investigators to know the answers.
But in a phone interview with NBC 5 Investigates, safety expert Scott Weldon said the investigation would likely examine Sunday's extreme weather conditions – with winds gusting to nearly 70 mph – and on how the crane was supported.
"It should have been able to withstand a 70 mph wind," said Weldon, president of American Crane & Safety.
"But I'm wondering if the gust, and the switching of the wind, didn't help create the problem," he said.
Weldon added that investigators in Dallas would likely look at whether the crane was rigged properly to withstand the winds.
"There's a lot of variables here that we don't know," he said. "My main question would be, where was the crane supposed to be supported?"
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Weldon said Bigge Crane and Rigging, the operator of the crane, is well respected in the industry, and has a solid safety record.
But over the last decade, OSHA has cited the company for 18 safety violations, some of which Bigge is still contesting.
In one high profile case, a worker died at an Arkansas nuclear power plant in 2013 when a crane erected by Bigge collapsed.
An OSHA investigation found that the company failed to ensure the crane was properly installed.
Bigge contested OSHA's findings, and the fines in the case were cut in half in a settlement.
A spokesman for the company told NBC 5 Investigates it could not immediately comment on its past safety record.
In a statement, it said: "Our thoughts and prayers are with the families of those who were killed and injured, and to those that suffered property damage. We are mobilizing personnel to the site to find out more and, of course, to fully cooperate with investigating authorities."