(Portland, OR) -- Mayor Ted Wheeler is pleading with protesters to put an end to destructive demonstrations in the city. Wheeler spoke at a news conference yesterday with Portland Police Chief Chuck Lovell and other officials. Demonstrations at police buildings this week have ended with some protesters lighting fires and vandalizing precincts. Wheeler is urging peaceful protesters to intervene when others engage in destructive behavior or to avoid areas where destruction is likely to occur. Wheeler adds that protesters engaging in destructive behavior risk being used as a "prop" in President Trump's re-election campaign advertisements.