Of course, it WILL be waiting for you in the car as you go to leave. If you try to run away, always take the bus. If you take a car the monster will be in it. Cabbies are always demonically possessed. And you have to go through dark, underground stations to get on a subway.
Monsters only attack overly horny teenagers.
Children can NOT be killed in a movie, only possessed or absorbed. If you've beaten the monster into a bloody pulp and you're sure he must be dead, take the opportunity to dismember, burn, eat, blow up or otherwise destroy him. Just tell them to run as you go by. If they're really your friend they'll follow. If not - that's their tough luck.