Three veteran members of the Chicago Police Department have been indicted for their roles in covering up the murder of Laquan McDonald.

Det. David March and officers Joseph Walsh and Thomas Gaffney were charged with conspiracy, official misconduct and obstruction of justice for allegedly attempting to prevent or shape the investigation, NBC Chicago reports.

“The indictment makes clear that these defendants did more than merely obey an unofficial ‘code of silence,’ rather it alleges that they lied about what occurred to prevent independent criminal investigators from learning the truth,” Special prosecutor Patricia Brown Holmes announced in a press release.

All three officers were on the scene on Oct. 20, 2014, when Officer Jason Van Dyke fired 16 fatal shots at 17-year-old McDonald, according to Holmes.