A Border Patrol union fired back at the American Civil Liberties Union (ACLU) on Wednesday after the left-wing organization condemned moves by agents to deal with illegal migrants who had allegedly assaulted them.

"We read this morning that the ACLU is upset that BP agents have the audacity to defend themselves," the National Border Patrol Council tweeted.

"We have a response for them. Go to hell."

The union was responding after the ACLU expressed outrage over an incident that took place Monday and was partially caught on camera. The group of Venezuelan migrants illegally crossing into El Paso, Texas, as they waved an enormous flag. Agents can be seen pushing migrants back into the river while firing pepper balls near them to control the crowd.

ILLEGAL MIGRANTS WAVE VENEZUELAN FLAG AFTER CROSSING US SOUTHERN BORDER, ATTACK BORDER PATROL AGENTS 

In a statement, CBP said a group of Venezuelans had attempted to illegally enter the U.S. while protesting along the Rio Grande’s international boundary.

The agency said one of the protesters assaulted an agent with a flagpole while another threw a rock at agents, injuring one in the process. That, in turn, led the Border Patrol to initiate crowd-control measures.

"These measures included the use of the authorized less-lethal force pepperball launching system," the statement said. "The crowd then dispersed and returned to Mexico."

CBP has said that its Office of Professional Responsibility is reviewing the incident.

ICE LAUNCHES ‘TAKEDOWN’ OPERATION IN GUATEMALA TO NAB HUMAN SMUGGLERS AND CORRUPT COPS, RESCUE MIGRANTS 

The ACLU called the incident "the latest in a long line of abuses carried out by CBP."

"Our government's failed attempts at preventing people from seeking protection in the U.S. lead to death and suffering. The Biden administration must restore a humane process for seeking asylum," the group said.

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The incident comes amid a continued flood of illegal migration across the U.S. border. There were more than 2.3 million migrant encounters in FY 2022, and more than 227,000 in September. Fox News cameras this week have seen a number of large groups of migrants coming across the border.

In just the Del Rio Sector alone, Border Patrol reports more than 50 large groups of more than 100 migrants since the beginning of October.

Fox News' Bill Melugin contributed to this report.