He looked like a Dennis.
So far I've come up with three possible scenarios that could have led up to this point:
ONE: Dennis has always been a workaholic which has put a significant strain on his family relationships, particularly with his son Drake, who resents the fact that his dad has never made it to a single one of his basketball games. Dennis planned to turn things around tonight by showing up at the championship game with a big poster board sign with Drake's name and number on it. He left work early so that he could pick up a box of Sharpies, but on the way to the office supply store he was hit head-on by another driver who had lost control of her vehicle. Dennis managed to pull the unconscious woman from the mangled hunk of steel just before it burst into flames. After waiting for what seemed like hours for emergency medical services to arrive, he is now racing to try to make it to the game before the final buzzer. All hope of reconciliation hangs in the balance.
TWO: In a classic case of mistaken identity, Dennis has been confused with an international super spy who was recently exposed as a double agent and is now on the run from a particularly surly Latvian mafioso. What Dennis doesn't know is that the murderous Vilhelms realized his mistake six blocks ago and decided to stop for a meatball sub instead of continuing to pursue him.
This storyline could also dovetail nicely with scenario #1.
THREE: Dennis is a running enthusiast who is training for the BriefChase, a themed half marathon in which all participants must dress in business professional attire. In preparation for the race, Dennis has decided to test out a different suit each day in the hope of finding the perfect combination of mobility and style.
Given the city I live in, my money's on #3.
If anyone has a more probable explanation, I'm all ears.