Per CNN:

Jeffrey Williams was arrested late Saturday, and he has been charged with two counts of first-degree assault, a count of firing a weapon from a vehicle and three counts of armed criminal activity, St. Louis County Prosecuting Attorney Bob McCulloch said at a news conference in Clayton.
“The demonstrations were pretty much over (when the officers were shot). People were leaving, and that’s when this happened,” he said, describing Williams as a demonstrator who had taken part in protests on numerous occasions.

Later in the story, there is this from the aforementioned Bishop Robinson:

Bishop Derrick Robinson, an area organizer, challenged the idea that Williams was a well-known protester.
“I asked him (Williams) why would he say that he was a protester because it makes us look bad — because so many things that we’ve done to rebuild our community. It sets us like five steps back to say that it was a protester who did it, but he admitted to me that he’d never protested,” said Robinson, who spoke to Williams on Sunday.
Robinson added: “We won’t allow this to distract us from our mission, and from purpose, because we will continue to fight.”

This has been the message from President Obama on down — let’s not allow the shootings of police office to distract from the important work of protesting and maligning police officers.