PHILADELPHIA - September 22, 2012 --The cash reward has just gone up for information in a brutal crime from last year. 23-year-old Iris Tyson was the subject of a massive search as family and friends handed out fliers of the missing woman. Her parents reported her missing on Mother's Day, May 8, 2011 when she went out to buy a Mother's Day gift. Seven days later, on May 15th, her body was found in a vacant lot between Sydenham and Hick Streets in South Philadelphia. She died from blunt force trauma to the head. Tyson's mother vowed to find her daughter's killer. "We are going to find you. "We're not going to stop. I'm never going to stop," said Kelly Tyson. When police ruled her death a homicide, the Citizens Crime Commission put up a $3,500 reward. Now the city of Philadelphia is posting up to $20,000 for any information that leads to an arrest and conviction. "Somebody saw that body and made that tip call to police. We need you to step up to the plate," said Santo Montecalvo. "We need you top pick up the phone. We need you to call 215-564-TIPS; that's the Citizens Crime Commission, or the Philadelphia Police at 215-686-TIPS. That call could be worth $23,500.