1 arrest made after Capitol Police clash with protesters outside DNC

One arrest was made for assault on an officer Wednesday night outside of the Democratic National Committee in Washington, D.C., according to Capitol Police.

Capitol Police said they had to "keep back" 150 people who were "illegally and violently" protesting.

Six officers sustained injuries from encounters with the demonstrators, "ranging from minor cuts to being pepper sprayed to being punched," according to Capitol Police.

All officers were treated on the scene, a law enforcement source confirmed to ABC News.

Members of Congress were hearing from prospective candidates inside of the DNC when Capitol Police evacuated them from the building, Congressman Brad Sherman, D-Cailf. told ABC News in a phone interview.

In total, about seven members of Congress were inside when they were evacuated from the building by "heavily armed and serious" U.S. Capitol Police officers, Sherman said.