On May 12, he and a senior U.S. Embassy official were nearing the end of their mission in Iraq and had gone to pay a goodbye visit to some journalists in central Baghdad.
As they left, according to Iraqi police reports and witnesses at the scene, their Blackwater convoy - which included two armored Humvees - sped out from a side street out into the main road. An oncoming taxi driver braked hard, trying to slow down, when one of the Blackwater guards opened up with his automatic weapon.
Bullets ripped through the Opel taxi, wounding the driver, Mohammed Nouri Hattab, in the shoulder. Yas Ali Mohammed Yassiri, who was in the back seat, died instantly. The convoy didn't even stop.
Later, both Blackwater and an investigation by the Diplomatic Security Service concluded that the guard had not followed correct procedure in giving the driver enough warning. He was sent home.
CBS News found Adam Hobson back in the United States and studying law in at the University of Pennsylvania.
Below is an edited transcript of his interview about that incident:
Hobson: I think about it everyday. It's by far the worst thing that's ever happened to me. Definitely the worst thing that happened to me out there.
As we left the compound, I remember the convoy stopped for a second, and we heard shots, but then we moved on. I remember seeing through the window a car with bullet holes in the hood. It was only once we got back to the Embassy that I found out that a civilian had been killed.
CBS: The guard in this case was found to be at fault, but he was simply sent home. Was that adequate punishment for killing an innocent civilian?
Hobson: In that particular case I don't know, because I just don't know exactly what happened. We definitely knew working over there that there was a gap. There was no mechanism in place for criminal prosecution. I don't know if in this situation [where the young man in the taxi died] the guard was criminally responsible or not. I don't think it was an intentional killing by any means, but we all knew that even if it had been an intentional killing, the repercussions might have been the same.
CBS: Was it inevitable that civilians would get killed by private security contractors?
Hobson: To move around the city we had to have guards protecting us. That did carry the risk of civilian deaths. I don't think it happened a lot but we did know that it happened.
You have to realize that every time anybody from the U.S. Embassy left the Green Zone, they were a huge target so we needed very heavy protection.
CBS: Was Blackwater too aggressive?
Hobson: I can't emphasize how much the team that protected me was extremely professional and extremely brave. Our lives were in their hands. Their job was to get us back safely and they did.
These guys would have only a split second to decide if a car coming at us was a suicide bomber or not. They had to make those judgments in a matter of seconds, and it wasn't always going to be right.
CBS: Should anything be changed in the way private security contractors in Iraq operate?
Hobson: Well, what happens when they don't operate correctly? What incentive do they have to operate correctly if there is no oversight? I think that's what the real problem is.
If someone in the military over there does something illegal, if someone in the State Department does something illegal - then they're held responsible in the United States. I think you need some sort of legal mechanism for contractors too.
CBS: How did having this aggressive security detail affect your work in Iraq?
Hobson: Every time we went out there was a huge cost - just in alienating people. Even if no shots were fired, we were driving down the wrong side of the road; we were stopping traffic. People don't like that. That's why we never made the decision to go out lightly.
CBS: Does your conscience ever trouble you now about that day when the man died?
Hobson: Yes. I think about it every day. That's when I really understood. I went to a meeting and somebody died because of it. It made meetings in the future a lot less important. In fact, I never left the [Embassy] compound again.