According to Marks' mother he was upset about his diagnosis, reported People magazine quoting Chicago Tribune.
"He couldn't bear the thought of another diagnosis. He was just coming to accept the diagnosis of bipolar," said Marks's mother, Paulette Mitchell.
Mitchell said she stayed with Marks most of Friday after picking him from a hospital but left him briefly to get her daughter from school.
Hours later, she received a call from her brother that Marks was walking in an alley with a gun.
Marks, a self-taught cook, lost to Christine Ha during the season three of the cooking reality show but according to his father there were no signs of mental illness while he shot for the show.
He, however, feels losing the show came as a big blow to Marks.
