Santa Monica police say pro- and anti-Trump demonstrators were shouting at each other Saturday when a scuffle broke out.
A video posted online shows a man wearing a "Make America Great Again" hat circling the crowd and then unleashing a torrent of spray from a canister. Officials say nobody was seriously hurt by the repellent, which is similar to pepper sprays used by police.
The Los Angeles Times reports authorities arrested a man who could face charges including violating the terms of his parole from a previous weapons violation. His name was not released.
Investigators are trying to determine whether a second man also sprayed the crowd.
Information from: Los Angeles Times, http://www.latimes.com/