I thought the dad should have called up Kal Penn for the address, and taken the gun that the man he killed had tried to use on him. Wander back home and open the door crying that he has been hurt, we need to change plans. Kal Penn was already almost in shock from his wound and the painkillers, and just walk up behind him (he has no reason to think dad had a gun) and just shoot him in the head.
Call the cops and tell them you have a part of a weapon that terrorists want to use, and the address where it's supposed to be delivered.
Dad had free access to a gun and wimped out. Kal wouldn't have seen it coming.
He would have done that, but he got signed on to a wimpy "non-hero" role.
Ahhhh...but then that might not work with next weeks script.