Some of them must have been, but by no means all.
At 01:11 , the Muslim journalist and women's rights activist Dr Qanta Ahmed, who was invited to the 45-min screening of the atrocities, says it's clear that hundreds and perhaps thousands of civilians repeatedly crossed the border to participate in the 7 October attacks.
From 07:24 , a survivor of the Nova festival describes most of the looting and raping being carried out by ordinary Gazan civilians. Hamas wore bulletproof vests and carried guns, but the rest were "people just like you and me, in blue jeans and sneakers," who flooded in with pickup trucks etc. At 15:24, she repeatedly emphasizes that it was civilians who raped and burned women alive.
At 01:30 , another Nova survivor, refers to "the terrorists" and then corrects himself to "people from Gaza" when describing the way they raped and butchered girls, either stabbing them to death after/during the rape or before it. They used knives, not guns.
I suspect it was the civilians who took the scalps, eyes, limbs, lips, breasts etc back to Gaza, to show off as hunting trophies, like Shani Louk's body. The predatory excitement is visible and audible e.g. . How many of these look like trained Hamas operatives to you?