O'Brien (Heian)

"I don't miss! I never miss!"

- O'Brian

O'Brian was a member of the UNSC Marine Corps who participated in the Human-Covenant War. He was an Orbital Drop Shock Trooper assigned to the Marine contingent aboard the Destroyer DD-993.

Assassination
He and his fellow Helljumpers were charged with attacking a Covenant force on an unnamed planet, in which O'Brian was to serve as the backup sniper. He felt this was an insult to his abilities and was even more shocked to learn that a Spartan-II was the primary shooter. As soon as they were deployed his pod was sent crashing to a nearby cliff and fell inot a swamp, the fall damaged the oxygen tank and with the pod sinking, it would have killed him. Cortez and Dutch tried to hurry to save him, but Cal calmly walks to the pod and with someeffort, lifts the pod and tosses it out of the swamp and then prying the door loose to get him out alive..

O'Brian is shocked by the sudden action and is not happy with the lose of Checkman when informed of his squadmate's death in their insertion run to the planet, along the way he needled Cal whenever the chance came, showing his contempt for the Spartan despite the fact that without Cal's help he would have died in his pod earlier.

During the operation, he is attacked by a Brute Chieftain that was wielding a Gravity Hammer as he kills a Grunt that he had tried to sneak upon but alerted when stepping n a twig, and is almost killed. However, before the Gravity Hammer struck Cal-141 saves him, but O'Brian winds up hanging over a waterfall as he watches the Spartan battle the creature, but loses his Sniper Rifle in the process along with his SMG, leaving him weaponless..

Cal saves him again when she pulls him up off the waterfall, he seemed unappreciative as he yelled at her to put him down, he snaps then at Dutch who told him to knock it off before all of the Covenant came down on them. His anger and contempt towards Cal grows a bit hotter when Dutch reminds him that Cal saved his life twice already and should thank the Spartan.

The group soon makes its way to where they're taking the shot as the shuttle of the Prophet was now touching down, as Cal is about to take the shot, O'Brian hoped that after all they had dealt with, Cal had better be as good as they said him to be. However, just the mission was reaching the end, the Chieftain from earlier returns, intent on slaying the ODSTs and the Spartan, and is about to kill O'Brian when Cal saves him again at the last second and for the last time, taking the blow from the Chieftain's Gravity Hammer.

The ODSTs tackled the Chieftain to the ground and Dutch shoots the Brute in the head, O'Brian is then shocked to discover that Cal was a woman and not a man as he and the others thought before when Cortez removes Cal's helmet to assess the extent of the Spartan's injuries. Cal, realizing that she can no longer function as a sniper due to extent of her injuries then yells to O'Brian to take the shot, at first he hesitates but takes up the Sniper rifle and takes out the Prophet.

He is then witness to the sight of Cal's last moments until she died, O'Brian is later seen back on the Destroyer, not saying a word before and after the rest of the squad angrily scold Berger who had mocked Cal's abilities in battle, and thinking deeply about how Cal continually saved his life.

Trivia

 * O'Brian bears a striking resemblance to Spike Spiegal from the anime, Cowboy Bebop.
 * O'Brian is one of the few known Humans to kill a Prophet.
 * It is possible that O'Brien later became a casualty during the first battle of Earth when a Pelican carrying a squad of ODSTs was shot down by a Covenant Scarab over Hotel Zanzibar, due to one of the ODST's stating after the crash that "O'Brien's down." However this is most likely just coincidence of names.