Ten people have been arrested on attempted murder charges after attackers in black military-style clothing opened fire outside a Texas immigration detention center in a “planned ambush” that left one police officer wounded, a prosecutor said.

The officer was shot in the neck on Friday, the night of the Fourth of July, after reporting to the Prairieland Detention Center in Alvarado, about 40 miles (65 kilometers) southwest of Dallas. He was treated at a hospital and released, the Johnson County Sheriff’s office said.

The shooting took place as President Donald Trump ’s administration ramps up deportations, which will be turbocharged by a massive spending bill that became law last week.

Initially, the attackers set off fireworks, and damaged cars and a guard structure by spray-painting “traitor” and ”ICE pig” on them. The attack “seemed to be designed” to draw U.S. Immigration and Customs Enforcement personnel outside the facility, “and it worked,” Nancy Larson, acting U.S. attorney for the Northern District of Texas, said at a Monday night news conference in Fort Worth.

Two unarmed corrections officers spoke to the group in the detention center’s parking lot as someone standing in nearby woods appeared to signal with a flashlight, according to a criminal complaint. Then the Alvarado police officer arrived and someone in the woods opened fire, Larson said.

“Another assailant, who was across the street, nowhere near the corrections officers, shot 20 to 30 rounds at these unarmed corrections officers,” she said. “There was an AR-style rifle found at the scene” that was jammed, she said. A flag saying “Resist fascism, fight oligarchy,” and flyers with words such as “Fight ICE terror with class war” also were recovered near the center.

The group fled. Sheriff’s deputies stopped seven people about 300 yards (275 meters) from where the officer was shot.

“Some were wearing body armor, some were covered in mud, some were armed, and some had two-way radios on them,” Larson said.

“It was a planned ambush with the intent to kill ICE corrections officers,” she said.

Sheriff’s deputies also stopped a van leaving the area and found two AR-style rifles and a pistol, along with ballistic-style vests and a helmet, the complaint said.

The driver, the only person in the van, said he had been at the detention center. He said he had met some people online and drove some of them to the detention center from Dallas to “make some noise,” according to the complaint.

On Monday, a man with an assault rifle fired dozens of rounds at federal agents and a U.S. Border Patrol facility more than 400 miles (640 kilometers) south in McAllen, injuring a police officer. Authorities shot and killed the attacker.

Asked if the two shootings were connected, Larson said she could not comment because of the ongoing investigation.

Additional searches in Alvarado led to masks, goggles, tactical gloves, more body armor, weapons, spray paint and fireworks, Larson said.

An extra layer of protection has been provided for staff at the Prairieland center, said Josh Johnson, the acting Enforcement and Removal Operations field office director in Dallas.

The 10 men and women, most of them from the Dallas-Fort Worth area, have each been charged with three counts of attempted murder of a federal officer and three counts of discharging a firearm in relation to a crime of violence. Another person was charged with obstruction of justice and conspiracy for attempting to conceal and destroy evidence, Larson said.

U.S. District Court records do not list names of attorneys representing the group, or scheduled court appearances.