Jeremiah

From Saints Row Wiki

Jeremiah is a physicist in Stilwater. He is also a biker and he knows how to race.

[edit] Hitman (Saints Row 2)

He can be killed by The Protagonist, due to this character being on a hitman list.
Hang out in the Marina and Museum districts and he'll show up. Recommended to ride a bike, he will show up sooner and you can keep up with him.