A Texas woman on her way to visit her cancer-stricken friend was shot dead by a teenage carjacker over the weekend, authorities said. Marietta Allison was discovered lying on a northwest Houston sidewalk with a gunshot wound at around midnight Saturday morning,  KHOU 11 reported . Allison, the co-founder of her own travel company, was taken to a hospital but later died from her injuries. Darius DeWayne Hall, 18, was spotted by officers at around 1 a.m. driving around in the stolen vehicle,