The violence captured on camera outside the Turkish ambassador's residence on Tuesday was a "brutal attack on peaceful protesters," D.C.'s police chief said.
Speaking at a Wednesday news conference, police chief Peter Newsham said: "Yesterday afternoon, we witnessed what appeared to be a brutal attack on peaceful protesters at the Turkish ambassador's residence."
Newsham said 11 people and one police officer were injured.
The protests came the same day President Trump met with President Recep Tayyip Erdogan of Turkey at the White House.
According to multiple reports, the fighting was between supporters and critics of Erdogan.
Asked if Erdogan's bodyguards — as some reports have said — were involved, Newsham would only say police are in the preliminary stages of the investigation. They have "very good video" and are confident they will be able to identify "most of the assailants," he said.
In a news release, the police department also said the actions "stand in contrast to the First Amendment rights and principles we work tirelessly to protect each and every day."
The department said they will work with the United States State Department and United States Secret Service to "identify and hold all subjects accountable for their involvement in the altercation."
The violence captured the attention of Arizona Republican Sen. John McCain.
"This is the United States of America," McCain wrote on Twitter. "We do not do this here. There is no excuse for this kind of thuggish behavior."
The video showed bloodied people getting punched and kicked.