A sergeant with the Chicago Police Department reportedly died from a self-inflicted gunshot wound to the head, according to the Chicago Tribune.
Officers found the man unresponsive in his squad car Monday afternoon. He has not yet been identified.
"Devastating news as an on duty #ChicagoPolice officer has taken his own life this evening," police spokesman Anthony Guglielmi said on Twitter. "The supervisor in our mass transit section was discovered unresponsive by fellow officers. Our hearts are heavy and deepest condolences are with his family and fellow officers tonight."