Earlier today, a tourist helicopter with five people aboard dropped out of the air into the water of Pearl Harbor.

Shawn Winrich was right by the shoreline when the helicopter crashed just a few meters away from him.

“I was standing over there taking pictures, and the helicopter started coming in low and straight at me,” Winrich said in a video posted to his YouTube channel shortly after. “I got my video camera ready and shot the video. Right after the crash three individuals surfaced right away, another one seconds later, and a minor was retrieved a few minutes later, his condition is unknown.”

News reports say the minor, a 16 year-old boy, is now in in critical condition. Two other passengers, a 45-year-old woman and a 50-year-old man, were hospitalized but are listed as stable. The helicopter’s other two occupants only sustained minor injuries.

Helicopters are notoriously difficult to fly — they have to “beat the air into submission,” as the saying goes. The Bell-206B chopper was on a sightseeing tour when it abruptly dropped out of the air. The pilot appears to maneuver the craft closer to the shore before setting it down quickly in the water. According to Hawaii News Now, the National Transportation Safety Board is investigating the crash.

See the full video of the crash below:

Over on Reddit, commenters are speculating as to what caused the crash, which was unusually sudden.

Redditor iamkokonutz, who claims to be a professional helicopter pilot, walked through some of the theories surrounding the crash.

“Doesn’t ‘sound’ like an engine failure. Also judging by the steam coming from the engine before they got submerged that there wasn’t a lot of wind, and didn’t seem downwind, so not sure if Vortex Ring State would be the culprit,” he said in a Reddit comment.

The leading theory, according to iamkokonutz, appears to be main rotor drive failure — essentially, the all important top rotor stopped working. But he also remarked that there were “so many possibilities on this one,” and added that he, like most investigators, would need to see the National Transportation Safety Board report before knowing exactly what went wrong.

As redditor ElPlywood put it, “A helicopter is thousands of moving parts trying to get away from each other.”

Here’s Winrich’s full interview after the crash.

Photos via YouTube