I shut car off and can turn key but it will not come out?

My ignition key won't release suddenly today.I shut car off and can turn key but it won't come out. I can turn car back on and off. I tried moving forward and placing back in park several times and pushed hard on the brake and it release finally. I was able to go to the store and had no problem when I came home. Later on, today my daughter also had the same problem she went to work. No sign of difficulty but had the same problem getting the key out at home so we had her drive around and try again. Is it the brake pedal, the shift (automatic) ignition switch it self, a cable in the steering column?