Factual error: During the remote control car chase the bad guys' minivan drives directly over it at one point. From the view of the toy car, you can see a driveshaft running down the centre of the undercarriage, which would be impossible on a front-wheel-drive vehicle like the Nissan Quest they're driving, which use half axles to drive the front wheels.
Factual error: When the criminals are supposed to be in a San Francisco airport, the scene was quite obviously filmed in Chicago's O'Hare airport. They then cleverly catch a flight to Chicago, and then come out at a different part of the O'Hare airport.
Factual error: In real life (there are a couple of scenes like this) snow doesn't fall from the sky at the intensity it was from clear skies.
Answer: It was Jernigan who thought there was a woman in the shower and he couldn't take the risk that if it was a woman, that she would eventually get out and see intruders in the house and call for the police. The only option open to Jernigan would be to kill her so there'd be no witnesses.
No it was Beaupre who thought there was a woman in the house.
I've seen the movie and I can confirm that it was Jernigan who opened the shower curtain because he thought a woman was in the shower.