A man who went undercover in an Atlanta jail for 2 months learned something unexpected about gang life

But behind bars, rival gang members behave a little differently than they do on the outside. In fact, the biggest threat to gang members in jail often comes from within their own gang.

That's what Nate, one of the undercover participants on A&E's documentary series "60 Days In," learned during his stay at Fulton County Jail.

The show, now in its third season, follows nine volunteers who enter the jail for two months under false identities in order to expose problems from within the system.

"I didn't see any issues between opposing gangs," said Nate, who did not use his last name on the show. "Rival gangs tended to coexist."

Much more common was intra-gang violence between members of different branches, or sets, of the same gang, such as east-side Bloods and west-side Bloods. And the gangs would go to great lengths to conceal their internal disputes from the rest of the inmate population, Nate told Business Insider.

"The thing is, the gang doesn't want to show civilians that they are fighting within the gang," he said. "So what they do is they hold a meeting in a cell and make sure no civilians are around. Two individuals have them fight in the cell for a period of time — there's a set amount of time, and then it's squashed.

"They take care of it that way, and you never even know anything happened unless any of them have marks."

On the other hand, when occasional violence between rival gangs did erupt, there was no hiding it.

"If it was another gang, they'd take care of it in the outside so everyone would see it," Nate told Business Insider. "That way it would be a warning."

Intra-gang fights were arranged by the gang leaders, who were inmates with the most street credibility, or "stain," in the outside world, Nate said. The leaders would call other gang leaders on the outside and get the fight approved. Fights generally lasted 20 to 30 seconds depending on the gang, he said.

Any minor slight could provoke a fight, Nate said, from gossiping behind another gang member's back to publicly disrespecting them.

"You'd give it, like, a good four, five minutes after a fight, and everybody would be back to laughing, back to chilling," he said.

As many as 500 of the jail's 2,500 inmates are affiliated with gangs, according to data provided by chief jailer Col. Mark Adger. His staff goes to great lengths to ensure rival gang members do not get paired in cells together — a safe measure, considering inmates at Fulton County Jail spend 15 hours a day in their cells.

For new inmates, who are constantly being tested and provoked by those higher on the social ladder, the allure of a gang can be tough to resist.

"They desperately want to fit in to keep from being victimized, and the lifestyle starts to grow on them," Adger told Business Insider. "That is usually what happens when people come to jail."

Episode 2 of the third season of "60 Days In" airs tonight at 9 p.m. EST on A&E.