After walking around the corner and getting into the lab and retrieving the lab key.. exit out the front door and walk toward the brute. Once he gets in locking range fire a shot and run back towards the door you exited. When inside open the door and try to coax the brute in.. when he charges the door run through the lab and go out the other large door. The brute will run all the way around and into the lab.. go in the computer room and turn on the device.