New York — At the height of the evening rush in Brooklyn, Gilbert Drogheo took a subway ride that he didn't survive.

Drogheo, a 32-year-old electrician's apprentice and father of a 5-year-old daughter, was fatally shot in a crowded station by another man who said he wanted to apprehend him for assault. The shooter, William Groomes, wasn't a police officer — he was a 68-year-old former city jail guard who was licensed to carry a concealed weapon.

Despite the emergence of a cellphone video showing Groomes appearing to pursue Drogheo before the shooting, prosecutors declined last month to charge him. The decision has left Drogheo's grieving family dismayed and raised questions about the line separating self-defense from vigilantism.

"I've watched the video 100 times, and I still ask myself, 'Why wasn't he charged?'" said Drogheo's mother, Linda Rodriguez. "It makes me so angry. ... It's like he got away with murder."

Groomes, who retired in 1993, hasn't spoken publicly. However, his supporters say Drogheo was the aggressor and Groomes had a right to protect himself.

Groomes "is taking this very, very hard," said Norman Seabrook, president of the city jail union. "It's sad because he lives with this every day."

But Drogheo, Seabrook added, "brought it on himself."

The episode unfolded March 10 as Drogheo, a friend and Groomes rode in the same subway car headed to one of Brooklyn's busiest stations. Both sides agree there were angry words and a fight, but there are conflicting accounts about who was the instigator.

According to some witnesses, Drogheo — who has an arrest record but whose family said had gone straight — and his friend appeared intoxicated and were harassing other passengers, including Groomes. Some also say Drogheo raised his fist and threatened to "smoke" Groomes before the friend jumped him — something the friend has denied — prompting Groomes to use the butt of his gun to try to fight him off.

At least one witness recounted Drogheo pushing Groomes back into the train as he exited. Drogheo's supporters say he and the friend fled the train to get away from Groomes.

Groomes, by his own account, followed with his gun drawn at his side, planning to make an arrest. One videotape showing Groomes walking through the station has audio of an apparent bystander shouting, "Don't shoot!"

Another shows Groomes a few moments later, moving more slowly, when he encounters Drogheo at the top of a stairway near an exit. Prosecutors say it appears that Drogheo took a step toward Groomes before Groomes pushed Drogheo with his hand. A brief struggle ensues before a gunshot is heard, sending commuters into a panic.

Drogheo's supporters have accused Groomes of taking the law into his own hands when he could have walked away. They believe he caught a break because of his law enforcement background.

"I'd characterize him as a vigilante," said M.J. Williams, an attorney and member of the activist group NYC Shut it Down. Authorities, she added, "are protecting Groomes. I can't come to any other conclusion."

With Williams' help, Drogheo's family has circulated a petition demanding that District Attorney Kenneth Thompson reopen the case and present it to a grand jury.

Kenneth Taub, the head of the district attorney's homicide bureau who reviewed the evidence, said he understands why Drogheo's family has concerns.

"We are not a fan of Groomes' tactics," Taub said. "We wish he had chosen a different path."

But Taub also said the videos actually tied the DA's hands because they support the finding that there wasn't enough evidence to prove a crime was committed. Prosecutors concluded that the second video depicts a chance encounter after Groomes had given up trying to track down Drogheo and that Drogheo initiated a struggle that resulted in an accidental discharge.

"Initially people looked at the video and saw what they wanted to see," Taub said. "If you look at it more carefully, there are subtleties."

The fact that Groomes was carrying a gun wasn't unusual, Seabrook said. Retired jail guards get a document — known as a "good guy letter" — that allows them to get permits to buy personal weapons and carry them for self-protection.

Such explanations feel like empty excuses to Drogheo's family, which emerged from a meeting with Taub and other prosecutors last week still wanting answers. The family is scarred forever, said Elizabeth Arroyo, Drogheo's girlfriend and mother of his daughter.

Groomes "didn't have to kill him," Arroyo said. "I don't want anyone to forget that."