Cain is a colossus - 6-foot-4 and 240 pounds. He grew up in North Philadelphia, in a family big in number and stature. Five times when he was younger, he broke bones in his hands in fights, but he's 37 now, a father, a man of faith.
When he's out at night, Cain likes to leave one earbud out, because he wants to hear what is happening around him. But now he started taking in details from the street - whether any cars were passing, whether there was room to swing if he had to.
Usually Cain doesn't pay his safety any mind in his neighborhood. "Nobody has ever bothered me in the 10 years we've lived up here. I'm not thinking about the worst-case scenario."
As the group drew closer, Cain saw that they were teenagers. He kept his eyes on everyone's hands. His thoughts flashed to a young friend killed eight days before on Roumfort Road, a couple blocks away. Police say Terrell Holcomb, 21, was shot in the back of the head. Cain says his friend was robbed first.
"Oh hell," one teen with braids said to Cain. "What are you looking at?"
Cain kept moving, halfway through the group, then turned on his heels and faced the one who'd called him out.
"Youngster," he remembers saying, "the only way I'm looking at you is because you're looking at me."
The young man didn't like that answer. He reminded Cain that he was outnumbered. They could take whatever they wanted, leave him begging.
Cain held his ground. "You do what you got to do," he said. "But know that I'm going to get my hands on one of you, and the one I get a hold of, may God have mercy on your soul, because I'm not going by myself."
The leader sized up this hulk of a man with the deep, booming voice. "I see we have a tough guy here."
Later, Cain had misgivings about what he said next, but at the time he couldn't get thoughts of his wife, his daughter, and his son out of his head.
"I'm not a tough guy," he replied. "I'm something you probably don't have. I'm a full-time parent."
The words hung out there. One of the boys asked, "How do you know?" and called Cain a crazy old head.
The ringleader snapped, "You don't know nothing about me. I tell you what, suppose I shoot you now?"
Cain saw the gun.
He doesn't think he showed any fear, although he was trembling inside. He thought of his own father's advice, about how some times you can talk faster than people can think. He thought again of his family inside the house.
Cain tried laying one more lesson on the youths. "You don't want a moment of anger to take away the rest of your life," he said as he backed up slightly. "You kill me, somehow you're going to get caught."
"Just shoot him," someone yelled twice. So Cain pushed his luck. He challenged the ringleader to a fight, one on one.
He kept talking, about the old days, when you fought your best friend on the street, then shook hands and played ball together the next day.
One of the teens noticed Cain's eyes, and said he didn't like what he saw in them. Something formidable no one wanted to stir. They walked away.
Omar Cain sat outside his house for 20 minutes catching his breath. He told his wife what had happened, how he wasn't sure what had made the boys flinch.
Maybe they'd never met a real man before.
Contact columnist Daniel Rubin at 215-854-5917, firstname.lastname@example.org
or @danielrubin on Twitter. Read his blog at philly.com/blinq.