Mr O'Brien recalled how his old instincts kicked in the moment he reached the scene.
"They talk about going into a zone, and that's what happened," he told the Herald at his home yesterday.
Mr O'Brien described himself as a luckless ambulance officer who was first on the scene at the murder of Maramarua publican Chris Bush in 1987 - but rated May's crash as his worst ordeal.
"I've seen everything that everyone doesn't want to see but I've never seen anything as traumatic and severe all at one time."
Daniella Lekhno, 20, Roch Jauberty, 21, and Austin Brashears, 21, died at the scene.
Four others - Kathy Moldawer, Alys McAlphine, Emily Melton and Margaret (Meg) Theriault - were injured in the crash.
"I knew I had to protect my daughter and I sent her back down to the house," Mr O'Brien said.
His focus was such that he gave orders to another local resident who he knew well, realising only afterwards who he was.
The less severely-injured crash victims and fellow students were also sent to the house, where Michelle set about caring for them.
"I came back down to the house to do a secondary assessment on them but Michelle had already dealt with them," Mr O'Brien said with a proud smile.
"She'd gone around and washed the blood off some of them and put plasters on cuts, given them blankets and was massaging the shoulders of those who were in shock ... one of them was just shaking."
He said he would not be surprised if Michelle one day went on to a job where she cared for people - but believed the experience would have put her off following in his footsteps.
The driver, 20-year-old Stephen Houseman, who also received minor injuries, was convicted and discharged last month.
"I heard his cries of anguish when he was told of the outcome of the accident and it wouldn't have mattered what penalty the courts had put on him ... it wouldn't have come close to the pain he felt," Mr O'Brien said.
"I'm just so sorry for the guy and I don't think there's a single driver on our roads that can say they've managed to keep their vehicle between the two white lines at all times.
"For whatever reason, something distracted him, he went off the road and couldn't get out of trouble.
"It was inexperience, but they picked the best guy to drive."
Memories of the day remain raw for Mr O'Brien and his daughter.
"It's still uncomfortable but we rejoice in the improvements of Meg [Theriault]. Last week, she managed to walk down the hallway of a hospital unassisted for the first time."
Ms Theriault had planned to walk the crossing with the others that day, and she and Mr O'Brien have made a pact to complete the tramp together, "just as long as she doesn't go too fast for me".
"The others are also wanting to return but they've all got to put their lives back in order, they've got their own grief to deal with. But I'm sure we'll see them again."
Messages from the students will be read by police at this afternoon's ceremony, also being attended by representatives from Boston University and the United States consul.
Mr O'Brien felt he did not deserve an award, saying he was simply in the right place at the wrong time.
"I felt I'd already done my duties to society and I knew too many sad scenes already, but I was a Kiwi who was brought up to be mindful of others. For me, it was doing something I couldn't walk away from."
