I've been following this since it came up on one of my news feeds. Terrible event. I've heard his seat broke? If so, he may have tumbled into the water? Was a windy day Saturday and with the water temps dropping and not wearing a life jacket, it really would have been a bad situation.
I bought a Jackson fishing kayak late this year and had it out twice. I go out alone and always wear a low profile, self inflating life jacket, (don't even know you have it on). I was out the same Saturday as this tragic story on Keho, some of the waves coming up did make me stop and think from time to time that's for sure.
I got to work on Monday morning after hearing about this story and ordered a surfboard leash just in-case I ever did end up falling overboard, so at least I can't get separated from the yak. A guy just can't be too careful when you're out by yourself. This is so terrible for his family.