A 21-year-old man was fatally stabbed in Allston early Tuesday as a house party spiraled out of control, authorities and a witness said. The stabbing was the city’s first homicide of 2013.

Police arrested a suspect, Brian MacDonald, 24, of Allston, who was charged with murder in the fatal stabbing at 48 Pratt St., which occurred just before 2:45 a.m., according to police and prosecutors. He is scheduled to be arraigned Wednesday in Brighton District Court.