Sheriff Jim Hammond said "several suspects" are under investigation in an incident in which a Sheriff's flag was taken down at the County Jail on Walnut Street and later burned at Miller Park.
He said, "The incident started at the jail and continued on to Miller Park. Rather than involve two agencies, the Sheriff's Office will take the lead on it."
The sheriff said city police are cooperating in the investigation with Assistant Chief Zac McCullough overseeing its role.
Marie Mott, a protest leader, went on Facebook Live to acknowledge taking the flag and burning it.
Cameron Williams, another leader of nightly protests, is seen in a video burning the flag.
Sheriff Hammond said an American flag was also taken, but was not burned. It was found in some bushes.
He said members of the protest group surrounded a county patrol car at the jail sallyport and began kicking it. He said, "They did some slight damage."