What was the deal with Sean Pertwee? (spoilers)

For people who don't know who Sean Pertwee is, he was the senior policeman called Rob who was giving orders to Matt and Jim at the beginning.

He's only in two scenes of the film as far as I can remember. He's giving orders to Matt and Jim in one scene and then in the other Matt and Jim are in a boat and have just witnessed some sort of explosion at a nearby building.

Upon witnessing the explosion Matt and Jim panic a bit then Pertwee (Rob) sprints into the boat, and goes off in the boat while Matt and Jim call after him. He's never seen or referred to in the film again as far as I can tell.

So what was that all about? What was he doing?

He was heading in the direction of the explosion at the building. Was he rushing to get to the building to find out what was going on and help the people inside?

Or was he on the run from the zombies and leaving the other two behind because he wanted to save himself?

Or was there something else I missed?

It just seemed a bit odd that he was in that scene. I couldn't work out what it was there for.

I think there were two boats. I may be wrong, but I think one was powered by an engine (the one Pertwee took off in) and the other just had paddles. Was this scene just inserted so Matt and Jim had to struggle to get to the helicopter in a fairly useless boat with just a paddle?

If anyone knows or has any ideas, I'd love to hear your thoughts.