Montana State Police arrested two members of an environmental organization on Wednesday and accused them of trespassing in a closed area in West Yellowstone while they attempted to film a bison-hazing operation.

Police charged Buffalo Field Campaign project director Dan Brister with resisting arrest and obstructing a peace officer, and volunteer Pete Bugosko with obstructing a peace officer and criminal mischief. Bugosko allegedly kicked out the rear window of a police cruiser while officers arrested Brister.

Brister suffered facial lacerations and a head injury that required three staples while a Montana state trooper tried to subdue him, according to Buffalo Field Campaign spokeswoman Stephany Seay.

Police transported Brister to Bozeman Deaconess Hospital, where he was treated. Officers later released Brister at the Buffalo Field Campaign headquarters in West Yellowstone. Bugosko was taken to the state police jail in Bozeman.  As of Thursday afternoon, Seay was attempting to raise $3,000 bail to secure Bugosko’s release.

Seay said the incident started when Bugosko asked an officer to do a better job of controlling vehicles on Highway 191 as the U.S. Forest Service and the Montana State Department of Livestock attempted to move between 300 and 400 bison from an area near Hebgen Lake. The confrontation erupted into a yelling match and the two were arrested.

Tom Butler, a captain with the Montana Highway Patrol, said his officers had closed a portion of Highway 191 to keep the public safe as the other agencies moved the bison across the road and back into Yellowstone National Park. One trooper was tasked with patrolling the area to make sure people didn’t enter the closure area.

“He [the trooper] saw two members of the Buffalo Field Campaign inside the closed area,” Butler said. “He made contact with them and asked them to get outside the closed area and they ran into the timber [still inside the closed area]. He followed them into the timber and ultimately ended up arresting one of them and brought him back out to his patrol car.”

According to Butler, a female member of the Buffalo Field Campaign came out of the timber and left the closed area when Brister approached the officer’s patrol car.

“A second guy approached and refused to go outside the closed area,” Butler said. “He was placed under arrest. While he was being arrested, the first guy kicked the side window out of the patrol car. While this is going on, keep in mind that there are 300 buffalo coming.”