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, and an Orbital Drop Shock Trooper in the 105th ODST Division. Some time between 2542 and 2552, he was assigned to a squad led by MSgt Cortez, as a part of the Marine contingent aboard the Destroyer DD-993.

Assassination
He and his fellow Helljumpers were charged with attacking a Covenant force on Heian. O'Brian was to serve as the backup sniper in the mission. He felt this was an insult to his abilities and was even more shocked to learn that a Spartan-II was the primary shooter.

The squad was deployed to the planet using the cover of a meteor shower. Upon landing, O'Brian's pod was sent crashing to a nearby cliff and fell into 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 stopped short due to the thick mud. Cal calmly walked to the pod, and with some effort, lifted the pod and tossed it out of the swamp. She then pried the door loose to get him out alive. O'Brian was shocked by the sudden action and was not happy with the loss of his fellow squadmate, Checkman, who had died during atmospheric entry. 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 was attacked by a Jiralhanae Chieftain wielding a Gravity Hammer while attempting to kill a Grunt he alerted. However, before the Gravity Hammer struck, Cal-141 saved him, but O'Brian winded up hanging over a waterfall as he watched the Spartan battle the creature. O'Brian lost his Sniper Rifle in the process along with his SMG, leaving him weaponless.

Cal saved him again when she pulled him up off the waterfall. However, he seemed unappreciative as he yelled at her to put him down, and then snapped at Dutch who told him to quiet down before alerting anymore Covenant patrols. His anger and contempt towards Cal grew a bit hotter when Dutch reminded him that Cal saved his life twice already and should have thanked the Spartan.

The group soon made its way to where they were supposed to be taking the shot, just as the shuttle of the Prophet was touching down. However, just as the mission was reaching the end, the Chieftain from earlier returned, and was about to kill O'Brian before Cal saved 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 shot the Brute in the face repeatedly with his SMG. As Cortez removed Cal's helmet to assess the extent of the Spartan's injuries, O'Brian was then shocked to discover that Cal was, in fact, female. Cal, realizing that she could no longer function as a sniper due to extent of her injuries then yelled to O'Brian to take the shot. At first he hesitated, but took up the Sniper rifle and killed the Prophet.

He was then witness to the sight of Cal's last moments until she died. O'Brian was later seen back on the Destroyer, not saying a word before and after the rest of the squad angrily scolded 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 Spiegel from the anime series, Cowboy Bebop, particularly his hairstyle.
 * In the Another Day at the Beach cutscene, an ODST also named O'Brian makes a brief appearance. When the three Pelicans are shot down by a Scarab, one Pelican crashes and one ODST is heard to say "We've lost O'Brian". This may be the O'Brian from The Babysitter.