Since the First Atlantis Reconnaissance Team changed the nanite base code from the Central data core on Asuras, some of them were able to take a different persona at will. That particular one chose to take the appearance of Evan Lorne. He was supposedly part of what was left of Niam's faction, and worked for the Asuran copy of Dr. Keller (it is possible he was her second-in-command) and decided to leave Asuras, steal a Zero Point Module and built a copy of Atlantis, and manufacture nanite-based copies of Sheppard's team, to learn how to ascend, because the team wanted to find something known as a "soul".
When a probe crashed on Atlantis, from Oberoth, Lorne attempted to cover the whole thing up be destroying the probe, in order for the team to not get suspicious. However, that didn't work. Soon, the team were able to call their bluff. John Sheppard managed to fire a shot in his leg, but Lorne was able to repair what little damage it caused. However, the rest of the Asurans discovered the city attempted to destroy it. The team escaped, but all the Asurans, including him were most likely killed or destroyed in the process. (SGA: "This Mortal Coil")