The city of Chicago is preparing for more massive protests after authorities released video footage of a white police officer fatally shooting a Black teenager 16 times Tuesday.

The graphic video of Officer Jason Van Dyke firing at 17-year-old Laquan McDonald sparked immediate protests, and officials say more are expected.

Authorities took more than a year to share the footage and charge Van Dyke. He has since been charged with first-degree murder, and is currently being held at a Cook County jail facility.

The video’s release and the charge comes days after a judge ordered that the recording be made public by Wednesday.

Moments before its release, Mayor Rahm Emanuel urged residents and protesters to remain calm.

“[Residents] will have to make an important judgment about our city and ourselves and go forward.” He said the incident was a potential “moment of understanding and learning.”

Read more at Associated Press.