Continuity mistake: After the beast and David break the window and fall down they do so beside each other, but when they hit the ground they are separated by several feet.
Continuity mistake: During the fight between The Beast and David against the van. From the inside you can see the indented fist from David's punch, but the next shot looking at The Beast there is no dent in the van where there should be.
Continuity mistake: When Elijah first goes into Kevin's room, there are a pair of shoes under the foot of his bed. These shoes disappear when the shot cuts back and forth from Elijah and Kevin.
Answer: He's picking the locks on the doors, bypassing the keycards.