On Tuesday evening, 69-year-old William Groomes, a retired corrections officer, was riding a Brooklyn-bound 4 train when he got into a confrontation with two younger men. The specifics of their quarrel aren't totally clear, but two things are certain: Groomes shot Gilbert Drogheo dead, and he wasn't arrested for it. Why not?

According to Gregg Pinto, who served as an assistant district attorney in Brooklyn from 2007 to 2013 and now operates a private law practice, the answer has little to do with self-defense or anything else about the conflict itself. "I can't imagine that if this guy didn't have a [corrections officer] badge, he wouldn't have been arrested," Pinto told me yesterday. "In my opinion, NYPD is arrest first, ask questions later. The only time you don't arrest is if the person is somehow connected to the police."

Multiple eyewitnesses said that the trouble started as Groomes boarded the train at the Bowling Green station, where Drogheo, 32, and Joscelyn Evering, 28, blocked the door and verbally harassed Groomes as he stepped in. After an argument, the younger men turned physical—the New York Daily News reported that one of the men punched Groomes in the head; DNAinfo says Groomes was shoved down into an empty seat—and Groomes pulled out a gun. When Drogheo and Evering exited the train at Borough Hall, Groomes followed them.

That's the point where an eyewitness video obtained by CBS New York picks up. Groomes—the taller man in the video below—ascends the stairs to the station's mezzanine, where Drogheo is standing near a turnstile. Groomes approaches Drogheo and hits him in the face. The two men grapple, the gun goes off, and the camera pans away. Drogheo was rushed to Brooklyn Hospital Center, where he died.

[There was a video here]

Witnesses agree that Drogheo and Evering initiated the conflict on the train, and a certain amount of knee-jerk against a young guy who picked a fight with a 69-year-old is understandable. But watching the video, it's difficult to imagine a scenario in which Groomes wasn't the aggressor after the fight spilled into the station. Carrying a loaded gun, he deliberately moved toward Drogheo at the top of the stairs and threw the first punch of the scuffle that led to the gunfire.

"From the looks of that video, there's no reason to believe that it was self defense," ex-ADA Pinto said. He elaborated further in an email: "In New York, if you use deadly physical force to defend yourself (i.e., shooting someone), you have to reasonably believe that deadly physical force is about to be used on you. There's nothing in that video that looks like the shooter could have believed that he was in imminent danger of deadly physical force being used against him. In fact, the shooter looks like he was the aggressor."

In Pinto's opinion, the non-arrest may have been a matter of "professional courtesy" extended from one group of New York law enforcement agents to another. "The only possible explanation...is that they are taking it very slow because he is a corrections officer," Pinto wrote. "There is a professional courtesy that gets extended to anyone with a badge. You'll never hear the NYPD actually talk about it, but it exists as a sort of unwritten rule. I'm not saying he will get away with this because he's a corrections officer. But, he is getting the benefit of the doubt while they continue their investigation. If he was some random guy who didn't work for the city, he would be sitting in Rikers right now."

Even if Groomes is arrested eventually, which seems relatively likely—he is expected to be brought back to the police for additional questioning, CBS reported—the professional courtesy affords him numerous advantages. Pinto explains:

First and foremost, he gets to hire a lawyer and hunker down to come up with a strategy for his defense. They can watch the video that was released and decide whether self-defense is even a viable option. He can also line up a bail package (probably through a bond) so that he can make bail immediately if the judge decides to give him bail instead of remanding him. He can hide any evidence that he would not want the police to find, particularly anything on his cell phone that could blow up his self-defense claim by showing his state of mind that day. On a personal level, he gets a chance to be with his family one last time without being separated by prison bars. All of this is very difficult to do from Rikers Island. Also, assuming he doesn't go on the run, he can show that he is not a flight risk and his lawyer has a better chance of convincing the judge to set bail instead of remanding him.

But perhaps the most vivd illustration of Groomes' privilege as a former CO is the one arrest that police did make: Joscelyn Evering, who was charged with menacing and felony assault.

Image via David Rogers/Flickr. Contact the author at andy@gawker.com.