evidence: JERUSALEM (AP) — A Human Rights Watch investigation published Thursday said an Israeli attack on a Gaza building in October had no apparent militant target, but killed 106 civilians, including 54 children, making it an "apparent war crime." International law prohibits attacks on military targets that will likely cause disproportionate harm to civilians. The Oct. 31 attack was one of the deadliest since the start of the war nearly six months ago. Human Rights Watch says four separate strikes collapsed the Engineer’s Building in central Gaza, which was housing some 350 people, around a third of whom had fled their homes elsewhere in the territory. WATCH: José Andrés accuses Israel of deliberately targeting World Central Kitchen members Those killed included children playing soccer outside and residents charging phones in the first-floor grocery store, it said. Thirty-four women, 18 men and 54 children were killed in the strike, according to the group, which says it corroborated its list of the dead with Airwars, a London-based conflict monitor. The dead came from 22 families. One extended family, the Abu Said family, lost 23 relatives in the strike, it said.