OK.
Seems like it would be a good idea to laugh at his joke.
"Can you run faster than 1200 feet per second? Because that's the speed of the bullet that'll be chasing you."
BWAAAA HA HA HA HAAAAAAAAAAAA HAHAHAHHAAAA!!!
You really think that is the best way to reaction to a threat like that? I think its a good way to get a pair of handcuffs on ya and a trip in the back of a cruiser.