need some advice on a problem im having.

Hi everyone,as you can see im new here and im having a problem with my 2000 focus st.o k here it is....i parked the car and put the emergency brakes up then like a second or two later the engine started idling fast as if i was steping on the acelator but i wasnt.i also want to note that this only started to happen after i had my car taken to a local mechanic for replacing the front brakes.
if anyone has any ideas or sugestions on what to do it will be apreciated.
Thanx.