When he saw Tomahawk land on the guard he opened fire, not bothering with headshots due to the power of his weapon.

After the guards were dead, he came out from his hiding place and walked over to the door.  "Give me a few seconds," he said to Tomahawk as he hacked the lock.  As the door opened he realized he probably just have used a key card from one of the guards, not that it mattered now.  "Ok, we're in."

With no guards inside, he was able to access the computer and shut down all of the generators, locking them with a complex code so that they couldn't be started back up.  "There, they'll have to reload the computer from backups to get their reactors back online.  So, to max security area?"