A man suspected of killing at least two people during armed robberies this year has now been charged with the February shooting death of his mother.

Keith Gibson was arrested on June 8 after an armed robbery in Wilmington, Delaware — just days after he allegedly shot and killed Dunkin’ manager Christine Lugo, 41, during a robbery in North Philadelphia.

Gibson allegedly accosted Lugo as she opened the store at about 5:30 a.m. on June 5, as CrimeOnline previously reported. Police said that later that day, he shot and wounded a 19-year-0ld in Wilmington and pistol-whipped an employee at a drug store in New Castle, CBS Philly reported.

Police in Elsmere, Delaware, believe he is responsible for the shooting death of Metro PCS store manager Leslie Lizet Basilio during a robbery on May 15.

Christine Gibson, the suspect’s mother, was shot and killed while at work in East Falls, Pennsylvania, on February 8, CBS Philly said. Linda Osuigwe, a friend and colleague who found her body, said friends and family were suspicious of her son, “but we had no proof.”

According to Fox 29, Philadelphia police are also looking to see if Gibson is responsible for the shooting deaths of two men at the Al Madinah Trading Shop.

When he was arrested after the June 8 robbery, officers seized a .357 revolver, and crime lab analysts are studying ballistics evidence. Meanwhile, sources told Fox 29 that investigators found evidence at Gibson’s Philadelphia home — which he previously shared with his mother — that may link him to at least one of the murders in Delaware, including that of Basilio.

Philadelphia District Attorney Larry Krasner approved the murder charges for Christine Gibson’s death on Wednesday, CBS Philly said. Gibson is currently being held in Delaware.

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[Featured image: Screenshot from Philadelphia Police Department vide0 showing suspect in murder of Dunkin manager Christine Lugo]