First of all, you have to know that everyone in this video is okay (you can tell by the clapping and laughing at the end). Knowing that everyone's fine, however, doesn't stop what's happening from being fucking terrifying. Here's a trainee throwing a grenade for the first time (see her being trained right before; how can you even think with a grenade in your hand for the first time?) and instead of tossing it blithely away, causing an explosion far in the distance, as you would see in the movies, she swings her arm and throws it completely the wrong way and directly at her fellow trainees. (Thankfully, the grenade was only a smoke bomb.) (This time!)
Man, I can't even imagine how that feels, but I'm probably going to spend the rest of my day practicing my arm swing just in case.