(CNN) Whenever New York Gov. Andrew Cuomo hears of an aircraft hitting a building, the September 11 terror attacks immediately come to mind.
Monday was no different, when a helicopter crash-landed on the roof of 787 Seventh Ave. in midtown Manhattan.
"If you're a New Yorker, you have a level of PTSD from 9/11. And I remember that morning all too well," he said.
"So as soon as you hear an aircraft hit a building, my mind goes where every New Yorker's mind goes."
New York Mayor Bill de Blasio said nothing suggests the crash was a terror attack, although the cause is still under investigation. One person believed to be the pilot is dead.
But the initial minutes of confusion evoked the terror of the September 11 attacks for those inside the building.
Nathan Hutton, who works on the 29th floor of 787 Seventh Ave., said many people felt the building shake.
Initially, no one though much of the shaking, he said, "until security said, 'get out of the building,' then you got a little nervous."
"Do I want to be coming down a staircase if there is something bad that's happening?" Hutton said.
"We had no choice, we all got out. Everybody was somewhat calm, but they were nervous because that thought is in the back of your mind."