2003 Other Mitsubishi Models security system activated

Electrical problem
2003 Other Mitsubishi Models

this is my sisters car, and she is an ameteur at cars, my dad knows abit about cars, but not about this.
My sister got her shoes out of the car and tried to lock it, she tried a few times but it wouldnt lock, so she put the key in the door to lock, and then it beeped. It stopped, then it went off another 4 times.
The key can go into the ignition, but it wont let us start the car, it seems that it has locked the car. But we dont know how to fix it.
Help please