The first encounter of the groundhog is in (and on the roof [of]) BTC bank, Mission 1. They are taking hostages and robbing the bank. Many of the groundhogs are holding drills.
You will have to kill the groundhogs. It is part of the mission. You can skip fighting some pressing "skip puzzles" button in option. There will be a boss-like fight at the end. When the groundhogs are getting money and running with the big drill you have to operate the pizza delivery motorcycle and shoot the groundhogs. The last part is opening the door fully.