A weekend shooting in Springfield has turned into a homicide investigation. Police say 34-year-old William Serrano was shot seven times on the porch of a home in the city's Forest Park neighborhood at about 7 p.m. Sunday and later died at the hospital. Investigators say they are searching for a suspect they consider armed and dangerous. He was identified as 25-year-old Julio Leiva.  Police say he could be in Springfield or his other address is in Framinham.