There are new details about what happened before a helicopter went down in Lehigh County last month.
A report from the NTSB says a warning light indicating a low rotor speed came on, moments before the helicopter went down near Lehigh Valley International Airport.
A horn blast was also heard before the crash. The helicopter collided with a building shortly afterward.
The pilot and a passenger were hurt. They had just taken off from Lehigh Valley International Airport.
The pilot, Matt McMillan, suffered a traumatic brain injury and spinal fractures. His passenger escaped with minor injuries.
An examination by a Federal Aviation Administration inspector revealed that the helicopter came to rest in a grassy area on the side of the building.