A Harris County jail inmate awaiting trial on a murder charge allegedly beat a young illegal immigrant accused of robbing and fatally shooting a 14-year-old girl in the back as she was walking home on Aug. 6. Melvin Alvarado, 22, one of two men charged with capital murder in the death of Shatavia Anderson, was beaten Thursday evening, sustaining serious enough injuries to be hospitalized and receive stitches, said Alan Bernstein, of the Harris County Sheriff's Office. Accused in Alvarado's beating is Robert Williams, 38, Bernstein said.