A 17-year-old boy accused of killing his mother was ordered detained Saturday after prosecutors described an unprovoked shooting inside the family’s South Shore home.  The teen, Davion Pryor, was identified by his father as the person who shot and killed his 43-year-old mother, Tatanisha Jackson, inside her residence in the 6800 block of South Cornell Avenue Thursday afternoon, authorities told a Cook County judge during a detention hearing at the Leighton Criminal Court Building.  Pryor was charged as an adult with first-degree murder in connection with Jackson’s death, after turning himself into a police station in the 7000 block of South Cottage Grove Thursday night. He told officers he knew police were looking for him, according to court documents.  Prosecutors said Pryor shot his mother four times in the head at point-blank range, unprovoked. Jackson was taken to the University of Chicago Medical Center, where she was pronounced dead. The Cook County medical examiner’s office ruled her death a homicide.  In ordering Pryor detained, Judge David Kelly ruled that Pryor, who was on electronic monitoring for a pending juvenile case at the time of the shooting, had demonstrated an unwillingness or lack of capacity to comply with conditions short of detention.  The judge did allow for the teen to receive treatment while detained for an unspecified mental illness. Pryor returns to court next Friday.  [email protected]