This claim appears on The New York Times:
ON the night of Sept. 16, 1982, the Israeli military allowed a right-wing Lebanese militia to enter two Palestinian refugee camps in Beirut. In the ensuing three-day rampage, the militia, linked to the Maronite Christian Phalange Party, raped, killed and dismembered at least 800 civilians, while Israeli flares illuminated the camps’ narrow and darkened alleyways. Nearly all of the dead were women, children and elderly men.
Also, Al Jazeera English:
Between September 16-18, 1982, in the middle of Lebanon's civil war and a few months after Israel's invasion of the country, hundreds of members of the Phalange party - a Lebanese Christian militia - in collaboration with the Israeli army, slaughtered about 2,000 Palestinian refugees, mostly women, children, and the elderly, in the Sabra and Shatila refugee camp located in Beirut.
Were majority of those killed in the Sabra And Shatila Massacres women, children and the elderly?