This happens when someone with the wrong kind of personality (See DICKHEAD) is given any form of power or privilege they go completely nuts and develop into mini-Adolf-Hitlers, taking extreme pride and even joy in exercising their new found control over others.
Typical Power-Rush types can be found anywhere in the job world but most frequently in retail and food retail.
These people will usually grow into control-freaks as they get older. Just ignore them, hopefully they will get fired or still be working there in 20 years. They will probably beat their children for it too.
Matt the Saturday sales assistant just got promoted to supervisor, now he's on a Power-Rush and he's twice the ass he used to be.