system
Given the following post, respond as if you're commenting on Reddit:
human
[MiB] Why did Jay chase the alien in the beginning of the movie?

You never really get an explanation but it must have been big. I mean he had two uniformed cops and Jay who was in plain clothes. 

What did he do to get such a reaction from the NYPD?
gpt
I would bet carjacking, grand theft auto, trying to jack a ferry, or something else. All the registered aliens were trying to find a way off Earth as fast as possible because the Bug was coming, and he was probably cutting legal corners trying to get to a spacecraft.