Just my 2 cents, but it sounds to me like whomever did this had no clue what they where doing. So most likely young kids. Them type door handles are the easiest thing to unlock with a small flathead.
You can get it between the handle and door skin and sometimes never even leave a scratch. Super easy and someone good at it can do it just as fast as a key. Dsm's are terrible for this as the handles loosen up over time.