Not just mall cops, it's just people in general in any position of power. When I was young I used to host game servers for a community I created and liked to have a decent amount of people to administrate them and keep the games fun for everyone. There were people playing for months and always seemed reasonable and level headed and I'd see if they would be interested and most jumped at the chance to be more involved in the community. Every once in awhile though those reasonable and level headed individuals once they got some measure of authority went absolutely crazy and there's no indication of who it would be. People can be the exact opposite too, they clown around taking nothing seriously always trying to push boundaries, but then you give them some responsibility and suddenly they are the most responsible person you've ever met, they just needed a chance to show it.