Bloodstains in the dirty snow on the sidewalk in front of a Boyd Street house were testimony to another killing yesterday, two blocks from the AMC Market where store owner Manuel Monteiro was gunned down last Monday.

Michael Mack, a 21-year-old resident of Bowdoin Street in Dorchester, was found around 4:30 a.m. yesterday lying unconscious on the Boyd Street sidewalk with a bullet wound to the head. He died a half-hour later at Boston City Hospital.