Revealing mistake: When Tomas and Brenda are avoiding the big pile of stuff down in ground in the elevator, there are wires visible pulling them.
Revealing mistake: When the Gladers are hanging upside down by their feet, they are all wearing jackets and T-shirts. The jackets all dangle toward the floor due to gravity. The T-shirts - which are not tucked in - all remain in place, keeping their torsos completely covered.
Answer: He is one of the guards that works in the facility.