Jason Van Dyke, the white police officer who fired 16 shots at Laquan McDonald, a Black teenager, is guilty of second-degree murder, a jury announced on Friday.

The verdict indicates a milestone in Chicago police reform. Van Dyke is the first Chicago police officer found guilty of murder for an on-duty shooting in nearly 50 years. The prosecutor charged Van Dyke with first-degree murder of the 17-year-old, but gave jurors the option to convict him of second-degree murder.

The jury also convicted him of 16 counts of aggravated battery with a firearm, one count for each shot he fired.

Tensions were high as the trial played out in the last few weeks. This morning, activists surrounded the county courthouse, and additional police officers were stationed throughout the city in preparation for mass demonstrations should Van Dyke have been acquitted.

Eric Heath, associate vice president for safety and security, sent an e-mail to University students and staff ahead of the verdict this morning to address concerns about mass demonstrations.

“We recognize the range and depth of emotions for members of the University community, and considerations that some have raised about reports of planned demonstrations regardless of the verdict,” Heath said in the e-mail. “The Department of Safety and Security is monitoring and working closely with the City of Chicago [and] is prepared to quickly increase staffing if the need arises.”

The shooting went relatively unnoticed when it occurred in 2014. Shortly after the shooting, Jamie Kalven, a journalist based on the South Side, revealed the existence of a police dashboard camera that documented the shooting.

This revelation set off months of court battles to release the police footage, which City officials eventually released in 2015. Mayor Rahm Emanuel had refused to release the footage until a county judge ordered the City to do so. Emanuel said he was abiding by the City’s policy to keep videos private until prosecutors’ investigations were complete.

Discontent toward Emanuel increased following the release of the footage. In early September, he announced that he would not be running for a third term as mayor.