A man in his 20s has been shot to death in the city’s second homicide of the year, Providence police said. Officers were called to Chalkstone and River avenues after reports of gunfire just after 1 a.m. Friday. Police said they saw glass and blood on a sidewalk, but did not find the victim. Authorities were later called to Roger Williams Hospital after a report of a man being treated for a gunshot wound to his head. The victim was transferred to Rhode Island Hospital, where he was pronounced dead. Police have not released information on suspects or a motive. The city’s first homicide victim of the year, Nelson Sanchez, 24, of Providence, was shot to death in a car last week.