This newer jumper, with only 50-ish jumps at the time, tried exiting the plane without unfastening his seat belt. Uhhh... yeah... what else is there to say? No bueno.
This may sound weird to people from the US but there are places around the world that don’t require — or at least don’t enforce — the requirement that seat belts be worn during take-off. This jumper noted that the video is from 2015 and that his dropzone had just started requiring seat belts, so this was a new procedure for him at the time.
Had this jumper sat up to check his gear before the jump, he would likely have noticed that he still had his seat belt on.
This type of incident is a perfect example of why more experienced jumpers get annoyed when the back of the plane doesn’t get up until the red light comes on. Prior to the door being opened, it’s important to get up and ensure your pilot chute didn’t sneak out, your pin didn’t become dislodged, etc. It’s not certain that a gear check would have caught this issue — some longer seat belts still have enough slack for a person to get up — but that’s the type of thing that should become obvious pretty quickly during a gear check.
We’ve seen a new jumper intentionally make sure that their seat belt was still on before opening the door at 2,000 feet. When (calmly and politely) asked “What were you thinking?!?” the jumper didn’t understand what had happened; it turns out it was their first time opening the door and they were scared of falling out below hop and pop altitude. It seems like common sense, but it’s not really discussed in AFF and new jumpers may not understand how catastrophic it would be for a plane to have a parachute deploy while the jumper is still attached to their seat belt.