A gunman hidden within a group of black protesters shot at St. Louis County police officers on Sunday night following a protest about the death of Michael Brown one year ago.

One of the protesters was shot by police after he fired “a remarkable amount of gunfire” using a stolen handgun according to St. Louis County Police Chief Jon Belmar.  

“We cannot continue, we cannot talk about the good things that we have been talking about, if we are prevented from moving forward with this kind of violence,” he said.

Belmar insisted the people conducting the violence were not protesters.

“They were criminals; they weren’t protesters,” Chief Belmar said of the groups exchanging gunfire. “Protesters are the people out there talking about a way to effect change. We can’t afford to have this kind of violence, not only on a night like this, but any point in time if we’re going to move forward in the right direction.”

The gunfire began as Ferguson’s acting police chief, Andre Anderson, was speaking to reporters.  The gunman fired at police who pursued him following the initial volley of shots.

“The weekend’s events were peaceful and promoted a message of reconciliation and healing,” Attorney General Loretta E. Lynch said in a statement. “But incidents of violence, such as we saw last night, are contrary to both that message, along with everything that all of us, including this group, have worked to achieve over the past year.”