Why does Hulk attack the Black Widow?

On the helicarrier Banner becomes the Hulk against his will because of the pain and shock he had just experienced. So when he turned into the Hulk he attacked the first thing that he saw which was unfortunately the Black Widow. read more

Hulk attacks Black Widow, because he apparently has no sense of surroundings once flips the switch into Hulk mode. ok. But then why does Hulk later"smash" on command from Captain America.. read more

Black Widow happens to be next to him and even though both are on same team, he attacks her and then Thor. He becomes hostile to everyone on the ship. But later on, in the fight against Chitauri troops, Hulk is very comfortably self-controlled. read more