@Marianneconnell
From the info I read which I haven't confirmed elsewhere, he was seen to fall if his bike and bump his head (he was in a helmet) but was seen to get back on the bike. He then discarded his clothes some 15 min later and was seen cycling naked, then discarded bike. It seems likely he sustained a serious head injury in his fall, poor little note, and became confused.
It's such a dreadful tragedy. I was so hoping he would be found ok. A friend's son fell off his bike and got a head injury - despite helmet - and severe concussion recently; he completely lost his memory and was just saying the same things over and over. Fortunately he was with his brother and after an overnight in hospital is now at home recovering. I will never forget this boy, it's really got to me.