Philadelphia Mayor Michael Nutter criticized Amtrak train engineer Brandon Bostian, who was behind the controls of the train that derailed in Philadelphia Tuesday, by calling the decision to go more than twice the speed limit into a curve in the tracks “reckless.” The comment by Nutter, made Wednesday night to CNN, set up a war of words with the National Transportation Safety Board, which said the mayor’s statement was “inflammatory.”

“Clearly it was reckless in terms of the driving by the engineer. There’s no way in the world he should have been going that fast into the curve,” Nutter said on CNN's “The Situation Room” program. "I don’t know what was going on with him. I don’t know what was going on in the cab, but there’s really no excuse that can be offered, literally, unless he had a heart attack.”

Robert Sumwalt, an NTSB board member, accused Nutter of a rush to judgment. "You're not going to hear the NTSB making comments like that," Sumwalt said, according to CNN. "We want to get the facts before we start making judgments."

Sumwalt told the “Today” show Thursday morning that Bostian applied the brakes to the train moments before it derailed in the Port Richmond section of Philadelphia. He also told “CBS This Morning” Thursday that determining “the speed of the train was a very significant discovery,” but that there may have been reasons for the speed that had nothing to do with the recklessness that Nutter claimed. For instance, faulty brakes could have prevented Bostian from slowing down the train from 106 m.p.h. to 50 m.p.h. at the curve.

Bostian couldn’t recall what happened moments before the derailment and had “no explanation” for the crash, his lawyer told ABC News. The engineer suffered a concussion and leg injuries in the incident. While he spoke with investigators, he did not give a statement to local police. Sumwalt added that the NTSB is also looking to speak with Bostian.