Maybe the friends were on the side of the road waving their arms, thus distracting the officers attention from the fellow in the middle of the road?
It could still distract you enough to throw off your reaction time, and cause rather than prevent an accident if there wasn't a lot of time to react. It depends a lot on the exact circumstances.
We don't know much about what happened, and a lot of what we do know is coming from witnesses that don't sound very credible in this case.