In the original Men in Black movie, at the beginning of the movie Agent K and Agent D find the alien Mikey hiding among immigrants being brought into the United States illegally. K and D take him out of sight and reveal him to be an alien and interrogate him. Mikey seems calm and rational, however, an INS agent walks over the hill and Mikey freaks out and charges the agent, forcing K to shoot him.
Why would he turn violent all of a sudden and attack the agent? If he was already violent, why didn't he attack K or D immediately, where he would have a better chance of surviving?