So tazering the guy, then running him over is ok. 
Okay in the sense that the cop has limited options chasing a guy on a bike. He can't outrun him on foot, so he uses the vehicle. Having been in many a pursuit myself, it takes a constant reminder to not get tunnel vision, to not become more dangerous trying to catch the bad guy than the bad guy is.. In this case, the cop probably thought.. I can't open the door on the guy as I drive by, it will dent my unit and I'll have to answer for that.. I can taser the guy and he will likely crash to the ground but that's his problem and he shouldn't be running from me. In all likelyhood the injuries will be minor. The cop probably fully expected the guy to be farther ahead as he turned the corner, not laying in the road from crashing (not from the taser from my understanding).
So while it isnt the result sought after by the cop nor the suspect, the bad guy didnt mean to crash, the officer didnt mean to run him over. So I have no problems with the attempted tasing, and while tragic, believe running him over was an accident, brought upon the suspect by the suspects actions.
Personally, when I pursue people/vehicles, we have a policy in place that puts conditions on pursuits. We have a checklist so to speak
Nature of the crime
Age of the offender
Is the identity known
weather and light conditions
road conditions
other traffic/pedestrians present
and so on and so forth..
I probably would have chased the guy, having probable cause based on time of night, location where he was located, and his fleeing, that he was likely up to no good. I wouldn't have attempted a tasing because 1. Its not all that easy to tase a subject even when stationary as both prongs have to connect to be effective. 2. My buddies would have laughed at me. But I have enough experience that I don't get excited about them, I would leave enough room for stopping in the event of an unexpected crash, and if he got away, we'll catch him next time.
So yeah, the tasing and the running him over... I wouldn't have done it, but it's not so far out of reason that I would not understand it.