Italy's triumph was their first in the Six Nations since they beat Scotland two years ago, and coach Nick Mallett said the rarity of their victories made them all the more enjoyable.
The win came almost two years to the day that the Bulls beat Utah by six in the finale for Hall of Fame Jazz coach Jerry Sloan, who abruptly resigned the following afternoon.
Scott Vernon used his strength to beattwo United defenders to the ball inside the box and, when he turned it back into the six-yard box from the bye-line, Magennis headed home from four yards out.
The Bruins were down by two with 90 seconds left, scored twice in a 31-second span and beat Toronto another Original Six team in the league's 17th OT game of the postseason.