Madison, Wisc., police chief Mike Koval says it is “absolutely appropriate” for protesters to express their feelings after a police officer shot an African-American teenager Friday night, but he called for restraint and said an outside agency will investigate the fatal shooting.

Koval said the incident occurred after an officer, called to investigate a man jumping into traffic, followed the teenager to a nearby apartment and forced his way in after apparently hearing a disturbance, The Wisconsin State Journal reported.

Koval told reporters that the teenager “then assaulted my officer and in the context of mutual combat, the officer did draw his revolver and subsequently shot the subject.” He said more than one shot was fired.

A large crowd gathered at the scene, some carrying signs and shouting “black lives matter,” but dispersed during the early morning hours. The crowd included demonstrators and organizers from the Young, Gifted and Black Coalition, the Journal reported.

“In light of so much things that have happened not just across the country, but in our own community, it’s understandable that the reaction at the scene and of some of our citizens is extremely volatile, emotional and upsetting. And we understand that,” Koval said at a news briefing, “That’s absolutely appropriate under these circumstances. We would urge, obviously, that everyone exercise restraint, calm and allow the Division of Criminal Investigation to conduct their affairs.”

Under a new state law, the DCI, which is part of the Wisconsin department of justice, takes over police-involved shootings.

Although the victim was not named by police, WKOW-TV spoke to his mother, Andrea Irwin, who identified the 19-year-old as Tony Robinson.

“My son has never been a violent person,” Irwin said. “And to die in such a violent, violent way, it baffles me.”

Koval said Robinson, before the shooting, had allegedly assaulted an individual in the street before going back to his apartment.

As to whether Robinson was armed during the confrontation with the officer, Koval said initial findings “did not reflect a gun or anything of that nature that would have been used by the subject.”