The two forces met Saturday during the pro-Trump Patriot Day rally.
According to Buzzfeed News, 200-300 people were estimated to be involved in the demonstrations and initially gathered in a local city park area before spilling into the streets of downtown. Several Trump supporters said they also felt uncomfortable about those elements.
Trisha, who declined to state her last name after she received online threats for her participation in a previous protest, bandages Rudy McKay's head after he was injured in a clash between Trump supporters and counter-protesters in Berkeley.
The clash occurred at noon when the supporters of the President were carrying out a rally to celebrate their "Patriot Day" when anti-protesters, dressed in black and having their faces covered with masks, barged in and caused the fight. He said they were being audited.
Toward that end, police checked people's backpacks before allowing them into the park. Civic Center Park, about 250 police officers, including some from neighboring Oakland, eventually made their way by mid-afternoon Saturday to where Trump supporters and so-called "antifa", or anti-fascists who use fascist methods, were turning up the temperature. "We've staffed accordingly and are preparing for a number of different contingencies", he said.
Despite the disturbance and cancellation of a weekly farmer's market event, due to the event, a stand was still opened during the rallies. Only about two to three officers were present near the crossroads.
Police banned anything that could be used as a weapon - or had been in past rallies - such as pepper spray, mace, baseball bats and glass bottles.
The marches coincided with the traditional April 15 deadline for U.S. federal tax returns, though the filing date was pushed back two days this year.
Rallies in Berkeley were part of wider nationwide protests at more than 150 locations demanding that Trump disclose his tax returns.
In Waters's hometown of Los Angeles, demonstrators filled streets while chanting, "Donald Trump has got to go".
Among their placard messages: "Prove you have nothing to hide", "Donald Ducks his Fair Share", "No 1040, no peace" and "I pay for your golf trips".