It dawned with a sky that was so clear and blue, it seemed like you could see forever. It was a Saturday, so quiet, and it looked like it was going to be a beautiful day. In Israel, it was a religious holiday for Jews, too, so few people were working, or ready for what was about to happen.

Around 6:30 a.m., as the sun was coming up, tiny figures could be seen in the sky, coming from the west, coming closer. At the site of the Nova Music Festival in the south, in the Negev, some sirens started to sound, and the music stopped. Those in attendance looked up, and saw the killers on their motorized paragliders, coming towards them. They started to run, but it was already too late. Some other killers had arrived, too, in Toyota SUVs and wearing military fatigues and carrying GoPro digital cameras, to record what they were about to do.

An estimated 4,000 members of assorted terror groups — Hamas, the Popular Front for the Liberation of Palestine, others — spilled across the border, along with 2,000 or so Palestinian citizens. They broke through the fences in more than 100 locations, near army bases and kibbutz farm communities. The atrocities would last for hours: 1,200 murders of men, women, children and babies; more than 100 rapes of women and girls; 250 people taken hostage, including infants. Most of the murders would happen at Nova, to people in their teens and 20s.

They set fire to children and beheaded babies. They killed entire families. They raped a woman and hacked off her breasts; others, they raped and then filled their vaginas with nails or bullets. It went on like that for hours.

We know these things because Hamas live-streamed much of it on Telegram, or they kept footage that they uploaded later to social media. It showed them laughing and smiling and posing for selfies, the walls of the kibbutzim smeared with blood and viscera. Bodies of Jews sprawled behind them on the ground.

Not everyone they killed was a Jew. They killed non-Jews, too. But their main target, then and now, was Jews.

While the orgy of rape and murder was still underway, Hamas and its axis — Hezbollah, the Houthis, Iran, Qatar, Russia and China — flipped the switch on a massive, global propaganda campaign to justify the atrocities of Oct. 7, and to spread their homily of hate throughout Western democracy. Soon enough, via bots and fake accounts and conspiracy theories, the anti-Semitic hate was everywhere, like a snake. Licking at our windows, trying to get in.

It got in. It is here. Here, in the civilized world of 2024, which now very much resembles another time and place, when all of the world was dark.

Where did their hate, their anti-Semitism, come from? Why have so many — Generation Z and Millennials, in particular — embraced them, filling our streets and computer screens with things that we thought would never happen again?

I’ve written five books about racism and anti-Semitism, filed hundreds of newspaper columns and stories, and I’ve been on the receiving end of plenty of death threats from haters over the years. In all that time, I’ve formed the opinion that anti-Semitism is a shape-shifter. It isn’t practiced by one ideology — it’s embraced, at different times, by every ideology, right and left. It is an ideology unto itself, in fact, one that is older than capitalism, communism and all the other isms. It adapts; it changes with the times. It endures, like a pestilence for which we have no cure.

To me, it is a tumour that metastasizes when exposed to the many successes of the Jewish people. Resentment about the extraordinary resilience of their faith, resentment about their strength as a people, resentment about their obvious love for each other and God. The anti-Semites seethe with envy and then hate. They are losers and, like all losers, they hate perceived winners.

So: today, now. Lots of news stories and opinion columns will be published this weekend, recalling the horrors of Oct. 7, 2023. Many will express the hope that such a shoah, such a catastrophe, will never happen again. Some will even say it won’t.

Me, I don’t know anymore. All I can think about is the documentary filmmaker who came to see me a few weeks ago. He was doing a documentary about the history of anti-Semitism in Canada. Near the end, he told me he grew up with a Jewish mother who always told him to have a suitcase packed, in case the killers returned. In case he had to leave quickly.

But this is Canada, I said to him. It’s 2024. It’s not Germany in 1939.

“Yes,” he said, and then he took out his wallet, and then he pulled a small crucifix from it. He held it up. He was crying.

“This,” he said, “is so I can pretend not to be a Jew.”