An Aero Med helicopter briefly took off from, and then crashed in flames upon the helipad at Spectrum Health’s Butterworth Hospital in downtown Grand Rapids at approximately 10:58 a.m. on Thursday, billowing smoke into the air and forcing a major evacuation. A pilot and a Federal Aviation Administration inspector escaped and were treated for non-life-threatening injuries.

“We could see debris flying everywhere,” said Bruce Walters of Cedar Springs, whose son was being treated at the hospital. “I could see the blades flying off. The boom shook our entire room. Then we knew something horrible had happened.”

According to the National Transportation Safety Board, between 1998 and 2005, 75 people were killed in 89 medical helicopter crashes. 77 percent of those crashes occurred at night. But according to WOOD-TV’s Storm Team 8, flying condition’s during Thursday’s crash at Butterworth were ideal.

Grand Rapids Police has cordoned off debris from the incident, and the NTSB and FAA have launched a formal investigation.