They might take him "downtown" for questioning, but they can't hold him on anything, so it's not really worth the effort, especially when there's still plenty of chance to catch the jumper before he gets away.
Which I hope he did. Nothing like flaunting a victimless crime and getting away with it.
If the police wanted to get to the jumper, couldn't they basically jail his friend temporarily and basically say: Hey, we'll let you go when your friend turns himself in at the police station. :\ Would that be a problem ? Not that I wish for that to happen, but I could picture an office wanting to get back at someone jumping away from him like that. Now, this cop seemed reasonably calm, so perhaps he didn't do anything further with the case ?
Did you notice the cop speeding off at the end of the video?
See, when the guy jumped, the cop had two choices:
1, stick around, take the cameraman in for questioning, and track down the jumper through him, assuming that the cameraman is even friends with the jumper, and not just some passerby who happened to have a camera, or;
2, try and catch the jumper before he gets away, by heading down to the beach, a pretty good bet, unless the jumper was prepared for a quick get-away, either by boat or waiting car.
He clearly chose #2 as the more likely option to get him someone who was
actually breaking a law.