'11 Cali alarm won't stop

So my wife had an interesting experience today. She went shopping and when she came out to the car again, unlocked and opened the passenger door the alarm started. She locked and unlocked again and the alarm kept going. She started the car, but the alarm was still going. At this point she calls me and is ready to sell the car. She was getting more attention than she felt comfortable with and 'uncle humor' comments left and right.

I told to get in, start the car and drive to a nearby parking lot where I would come and meet her. When she started to drive the alarm stopped.

So why did the alarm not stop when pressing the keyfob?

I told it is part of the Italian charm ;-)