Broken Femur

My 50 year old neighbor is really into snowboarding and wanted to learn how to wakeboard so I took him out today. He got up on his third try and rode for about 80 feet. When he fell it looked like the board slid out in front of him and he landed on his back - it didn't look like an unusual fall. When I circled around to get him the rope, he seemed a little off and I asked him if he was okay and if he wanted another pull. He said he wanted one more. He started getting up and then just let go of the rope. He yelled for me to get back to him quickly and said he broke his leg. We could see his leg while he was still in the water and it was obvious that his femur was broken. We got him up onto the swim platform and he was in extreme pain. I didn't want to move him more than what was necessary, so instead of trying to get him out of the bindings, I just unscrewed the bindings from the board and left them on his feet. Luckily the rangers were driving nearby and I waved them down. They called the paramedics and cleared the boat ramp for me so we didn't need to wait for an opening. It took us about 8 minutes to get to the boat ramp driving slow so he didn't bounce around. The paramedics arrived just as we were pulling up to the ramp. They put him on a backboard and splinted his leg to keep it stabilized and gave him pain medication through an I.V.. They cut my prized Zeus bindings off his feet, which was sad but necessary. The rangers and paramedics were absolutely incredible, they couldn't have been better. I even noticed that one of the paramedics had even taken his boots off before getting on my boat - of course due to the circumstances it wouldn't have bother me if he had left his boots on but I really appreciated his thoughtfulness. The update from the hospital is that he will need to stay overnight and will need to get a rod in his leg.

So the reason for this post is this. This happened about 7 hours ago and I keep replaying it all in my head. I can't figure out how it was possible for his femur to break, especially since it didn't seem like he fell hard. It wasn't just a small fracture, his femur was broken in half. Anyone ever heard of a beginner breaking their femur wakeboarding? I could maybe see how someone could break their femur coming down wrong from an invert but not like this.