1. Call 911
2. Call 911
3. Call 911
#1, you are a guest in your folks house, wake up and see an "intruder"--maybe it's you're Dad coming downstairs to pee at night, old guys do that, (don't ask me how I know!). Pull a gun on Dad and you're living in your car. Locked doors in this case are better protection than a firearm.
#2, you are most likely going to escalate the situation by drawing on this goof, let him leave and call the police, only draw if your LIFE is in danger.
#3, police (in most jurisdictions) have been trained to calm such situations and also have backup and non-lethal methods to restrain such folks.