Dozens of demonstrators broke through a security fence near the United Center arena in Chicago on Monday evening, where the Democrats' convention is being held.
Several of the demonstrators, who made up a smaller part of a protest march for a ceasefire in the Gaza War, were arrested by the police.
When there are individuals who infiltrate a crowd with the intention of committing violent acts and vandalism, then we will act to stop them, says Larry Snelling of the Chicago police.
