Police said early Tuesday around two dozen people were arrested during protests overnight as demonstrations began to wind down and grow more peaceful. Officer Shawn McGuire said about 23 people were arrested, though police were still confirming official totals. The St. Louis County Police Department tweeted late Monday that some members of the crowd were unlawfully assembling and had started throwing frozen water bottles at officers. Some witnesses told the St. Louis Post-Dispatch that officers began deploying pepper spray. Earlier, the chief executive of St. Louis County declared a state of emergency while protesters blocked rush-hour traffic on the highway. The unrest began Sunday after police shot a man who they say opened fire on their vehicle. More than 1,000 people had gathered to mark the death of an unarmed black teenager who was shot and killed by a white officer a year ago.