I am almost afriad to post this after looking at what other people have posted about this but here it goes anyway.
I rear ended my mom the same way. She was getting ready to make a right turn on red (after a stop) and I was going to make it behind her some other car decided to make a U-turn (illegal at this intersection) right in front of her and she slammed on her brakes and I slammed on my brakes a second later and made a nice licence place screw head hole in her bumper.