Would you expect these dog to be killers?

Packs of dogs have occasionally been implicated in fatal attacks on humans. In one case in Philadelphia that occurred in the ealy eighties, a group of five household dogs ganged up and and mauled to death a 81 y.o. invalid lady. Animal behaviorist, Victoria Voith, an investigator on the case tested the dogs for their temperament. A striking finding that when the dogs were tested alone, each was non-aggressive; however, when placed back into their "pack", collectively they became very aggressive towards people,

Tha above photo was scanned from the text of Steven R. Lindsay, Applied Dog Behavior and Training, Vol. 2.