Unfortunately, that is not an isolated incident. Dirt bike forums are full of tales of booby-trapped trails set by eco-terrorist types. I ride once a year in the Colorado mountains and always have thoughts of sabotaged trails in the back of my mind. As trails usage gets more contentious among mountain bikers, horse riders, hikers, hunters, motorized vehicle off-road riders and "put it under glass and preserve it" types, these things will happen. Be careful out there, wear good protection and don't ride alone.
Probably some typical wacko Tree Huggers. They're no different then the Towel Head Terrorists. The only way to stop that kind of violence is to give them a taste of their own medicine. Possibly a public stoning!?
They need to be absolutely roasted. We have to have faith in the court system, as even though it is flawed, it is by Far and Away the best system anyone has ever constructed in the history of the world.
I've had two instances of eco-terroism perpetrated within a mile of my home. One was a trapping company set on fire and the other was a McDonalds that was under construction set on fire. (I'm not so sure that burning Mcdonalds' is such a bad idea though.) The same ecowackos were arrested for the crimes a few years later.
We've also had trouble with tourists near the Moab slickrock trails trying to run down dirtbikers/ATVers with their SUVs. Bunch a wackos. Never mind that the bicyclists have done tons more damage to those trails than motorcycles. Have you seen what hundreds of bicyclists dragging their wheels down sandstone do to the rock surface? It ain't pretty.
This is why I take my .44 Blackhawk (w/ 300 gr bear busters) when I go dirtbiking anywhere where the "environmentally conscious" might be. Goes right through that aluminum radiator and engine block.
In Rio de Janeiro I saw several motorbikes with a rigid antenna looking thingie in the front, with a hood where a small blade was attached. The explanation was that sometimes the kids in favelas flew kites, broken glass glued on the string, over the roads in order to slit open the throats of passing motorists. This was not done in spite but in order to rob them.
My guess in this case is also that these three fellows just wanted to rob the guy.
no kidding... there is a sport popular in a lot of areas around the world of flying kites with glass powder on the strings but the game is to cut the strings of the other kite flyers, not the throats of motorcyclists