Video: Mtb Bro Rams Dirt Biker
Usually, when videos like this surface, the collision is a result of a negligent or jerk off driver. In this case of two wheel on two wheel violence, Mr. Mtb was shredding a little too hard for this multi-use trail.
The Youtube user reports the bikers were cruising at around 30 mph around a blind turn when they crashed into the dirt bikers heading uphill. The lead mountain biker possibly suffered a broken arm from the crash.