SAN DIEGO >> Before the rise of social media, Border Patrol agents gathered in parking lots at the end of their shifts for what was known as “choir practice” — a chance to share what they saw that day and anything else on their minds.

T.J. Bonner, who led the National Border Patrol Council during much of his 32-year career as an agent, recalled the defunct tradition while trying to explain a secret Facebook group for agents that included sexually explicit posts about Rep. Alexandria Ocasio-Cortez and questioned the authenticity of a recent photo of a father and daughter who drowned in the Rio Grande.

“That outlet faded away and was replaced by social media, where people thought they had a safe place they could vent and process,” said Bonner, whose career ended in 2010 and who does not belong to the group. “That would explain some of the callous comments. The vile stuff? There’s no excuse. I’m certainly not going to try to defend it.”

Billed as “fun, serious and just work related,” the group boasts about 9,500 members. “We are family, first and foremost,” it states, according to ProPublica, which reported its existence on Monday, igniting fierce outcry.

A former agent who belongs to the group said Tuesday that members had to provide the administrator with their graduating class number from the Border Patrol Academy and have a current member vouch for their credentials. The agent, who retired last year in San Diego, spoke to The Associated Press on condition of anonymity because he feared a public backlash.

The agent likened the forum to a bar where agents would gather after work and swap stories. He said any agent active on Facebook would have likely received an invitation to join.

Some posts were graphic, doctored images of Ocasio-Cortez, including one that shows a smiling President Donald Trump forcing her head toward his crotch, according to screenshots obtained by ProPublica. Other comments refer to Ocasio-Cortez and fellow Democratic Rep. Veronica Escobar of Texas as “hoes,” and one member encouraged agents to throw a “burrito at these bitches.”

A news story about a 16-year-old Guatemalan migrant who died in Border Patrol custody in May elicited a response from one member, “If he dies, he dies.” Another member posted a GIF of the “Sesame Street” character Elmo with the quote “Oh well.”

The posts threaten to tarnish the Border Patrol’s image at one of the most challenging times in its 95-year history. Acting U.S. Homeland Security Secretary Kevin McAleenan today called the posts “disturbing” and “inexcusable” in a tweet and reiterated that an investigation into the page was planned.

“Most importantly, the words of these few individuals directly undermine public trust in the Border Patrol and the dedication and compassion with which the rest of you undertake your duties each and every day,” Provost wrote to staff.

George Allen, who retired in 2017 after a 31-year career, most recently as an assistant chief of the Border Patrol’s Tucson, Arizona, sector, said he had heard of the group, which is named “I’m a 10-15,” a reference to the agency’s internal code for “aliens in custody.” Although he was not a member, he belongs to another Facebook forum where the group has occasionally been mentioned.

“I’ve heard other agents talk about it,” Allen said. “The ones that talk about it talk about it in a negative manner. Some of the posts really bash the older agents.”

The political fallout revived criticism of the agency’s culture, which was a subject of extensive news coverage after a string of migrant deaths in Barack Obama’s presidency but faded from public view after Trump took office.

The National Border Patrol Council, an early supporter of Trump’s presidential bid whose leader, Brandon Judd, advises the White House on immigration, said Monday that it “strongly condemns” the posts and that they do a “great disservice to all Border Patrol agents, the overwhelming majority of whom perform their duties honorably.”

The union produces a radio show, “The Green Line,” that mixes discussions about border security with shoptalk and freewheeling news commentary. The hosts alternate between workplace gripes like radios that don’t work in remote areas and topics in the news. They have called the Black Lives Matter activists “domestic terrorists” and Mexico “a corrupt country.”

Gil Kerlikowske, who was commissioner of parent agency U.S. Customs and Border Protection from 2014 to 2017, riled the union by recruiting Mark Morgan from the FBI to be the first outsider to run the Border Patrol. Morgan was ousted during Trump’s first week in office but impressed Trump as a television commentator and was recently named acting commissioner of Customs and Border Protection, with union support this time.

“Changing culture is pretty difficult,” Kerlikowske said. “You can change the behavior to some extent. You can punish, suspend people. You can terminate people.”