“Stop, stop, stop!”

The audio recording from air traffic control moments before Air Canada Flight 8646 collided with a fire truck on the runway at New York’s LaGuardia airport is harrowing. The CCTV footage showing the impact — the aircraft striking the side of the truck, and then colliding nose-first into the runway, killing both pilots — is difficult to watch.

“Oh, God,” a voice can be heard whispering in the background of the video seconds before impact.

Investigators in the U.S. and Canada have cautioned that it is too early to determine a cause and that several safeguards would have had to fail for a disaster of this magnitude to occur.