How do you get tranquilizer gun sift heads world act 3

Its real easy ...

1. You go home to Vinnie's friend the man that can upgrade your weapons.

2. You walk into the room he is in ... ( second room in the house)

3. After the conversation you press the gun laying on the table next to him (That's the tranquiliser gun)

4. You go to the town hall and shoot down everyone in your way till you get to the mayor...

(Sorry for bad spelling)