any bike can be turned into a single speed. buy a decent ss kit (spacer and cog) and a tensioner, new front chainring and you are set. run an eno eccentric hub if you like it without tensioner. read the ss faq's.
What you need is to put a rear cog in line with a front chainring and have a chain tensioner. An ENO hub would be useless to you if your 69er is fully suspended. If it's a hardtail you could use the ENO and then you wouldn't need a tensioner. It depends how you want to do it and what bike you have.
Authorities speculate that speed may have been a factor. They are also holding gravity and inertia for questioning.
An ENO eccentric hub, while more expensive than the tensioner route, is less hassle in the long run. Great piece of equipment. With the help of a friend I converted a Cannondale F400 to a 69er singlespeed and used the ENO eccentric on the rear wheel. Worked great.