The Chicago Police Department announced that a second person has been charged in connection with the death of graduate student Amadou Cisse. Benjamin Williams, 21, of south suburban Dolton, was charged early Friday with first-degree murder for allegedly taking part in the killing of the 28-year-old Senegalese graduate student on Nov. 19.

Williams was also charged with three counts of armed robbery, one count of attempted robbery and one count of aggravated discharge of a weapon in connection with a series of incidents that included Cisse’s murder.

On Nov. 28, Eric Walker, 16, Chicago, was charged as an adult with first-degree murder and one count of attempted armed robbery with a firearm in connection with Cisse’s death. He was also charged with two counts of armed robbery with a firearm in connection with the incidents.

On Nov. 29, Demetrius Warren, 17, Chicago, was charged with three counts of armed robbery and one count of aggravated discharge of a weapon in connection with the incidents.