Authorities say the 20-year-old man charged in the shooting of two St. Louis area officers had been at the protest earlier that night.
St. Louis County Prosecutor Robert McCulloch said 20-year-old Jeffrey Williams is charged with two counts of first-degree assault, one count of firing a weapon from a vehicle and three counts of armed criminal action.
Williams is being held on $300,000 bond.
McCulloch said Williams already had a warrant out because he had violated his probation "for receiving stolen property."
McCulloch said the suspect "claims he had a bit of a dispute with some other people there" and wasn't aiming at the officers.
The prosecutor said they were still investigating the claim, but did admit there were civilians positioned between the shooter and the officers struck during the time of the shooting.
Officials said the arrest was made due to information received from the public.