On Saturday, in a planned protest that some worried would turn out to be “another Charlottesville,” hundreds of far-right demonstrators gathered in the city of Portland, Oregon, and were met by hundreds of counterprotesters.

The demonstrators said they were rallying to support the leader of the Patriot Prayer group, which has been behind contentious far-right rallies in several cities in the past couple years. Supporters of the far-right men’s group the Proud Boys also rallied in support.

But the clash turned out to be relatively nonviolent—there were just four arrests—and it was the Portland police who came under fire on social media afterward for their tactics. According to reports from the protests, the police were out in large numbers in downtown Portland and worked actively to keep the two groups separated. But, police said afterward, the crowds turned violent, and some protesters started throwing rocks and bottles at the officers.

“This was a dangerous situation for all those involved, including officers, and I am disheartened that this kind of illegal behavior occurred in our beautiful city,” Police Chief Danielle Outlaw said in a statement afterward.

Police then classified the protests as a “civil disturbance” and ordered the demonstrators to leave. When the protesters failed to do so, officers began firing flash-bang grenades and, according to some reports, rushing and sometimes shoving the crowd of counterprotesters. Eder Campuzano, a reporter for the Oregonian, was struck in the head during the clash and injured.

Was just standing next to @Oregonian reporter @edercampuzano, he got hit with something and is bleeding. Medics helping him. Things are getting extremely intense, even for those of us standing back from the center of these groups pic.twitter.com/F4ID7Dj2Zp — Tyler Dumont (@TylerDumontNews) August 4, 2018

One antifa protester also said one of the police flash-bang grenade canisters cut his head through his helmet. A friend of the victim told HuffPost that “he would be dead if he wasn’t wearing a helmet.”

People and groups, including the ACLU, quickly criticized police for being too aggressive toward the anti-fascist protesters in order to protect the far-right demonstrators.

On Sunday, the Portland police department released a statement announcing an investigation into any injuries that might have been caused by police. “This morning I learned of allegations of injury as a result of law enforcement action,” Outlaw said. “I take all force applications by members seriously and I have directed the Professional Standards Division to begin the intake process regarding these allegations to determine if force was used and if so, was within our policy and training guidelines.”

The Portland protests came just a week before the anniversary of the Unite the Right rally in Charlottesville, Virginia. To mark the occasion, white nationalists are planning an Aug. 12 rally in Washington, D.C. They are expected to be also met with counterprotesters.