Easy. Psycho has gun, tells you to leave or he'll kill you. You leave, thinking there'll be time to get help. You also leave because you believe in the basic goodness of (some) man, and maybe he told you he wouldn't hurt the kids, BUT HE DID SAY HE'D KILL YOU IF YOU DIDN'T LEAVE. You don't want to subject the kids to the vision of you -uh- being killed in front of them. So you leave. You know, either way, no matter what you do, you'll have to live with your decision for the rest of your life, no matter how short. But mostly you leave because you think you can get help.
signed,
a mother AND a teacher (who, btw, nowadays, would have been armed)
:-)