Even by the debased standards of the nihilistic, spiraling violence in the Mideast, the savage attack on worshipers at a Jerusalem synagogue on Tuesday was a heinous event. Armed with meat cleavers and guns, two Palestinian cousins from East Jerusalem, shouting "God is great," killed four men — three of whom were rabbis — who were praying along with others.

All four victims held dual citizenship, including three Americans — Aryeh Kupinsky, Kalman Levine and Moshe Twersky, who came from a prominent family of rabbinical scholars. The fourth, Avraham Goldberg, was a British citizen. Five other worshipers were wounded, as well as two Israeli police officers who engaged in a gun battle that killed the attackers, Odai Abed Abu Jamal and Gahssan Muhammad Abu Jamal. One officer, Zidan Saif, a father of a 4-month-old boy, later died, compounding the tragedy.

The butchery left blood spattered on sacred texts and clothing, underscoring the horror, as well as the fact that the attack was not random but instead targeted toward a religion. Israeli Prime Minister Benjamin Netanyahu ordered additional security measures and pledged that his government would "respond with a heavy hand."

That should also be the response from, and responsibility of, Palestinian President Mahmoud Abbas, who leads the ostensibly moderate Fatah, which governs the West Bank. While Abbas condemned the attack, he qualified his statement by calling for "the immediate cessation of the storming of Al-Aqsa Mosque complex by extremist Jewish settler groups as well as an end to provocations of settlers and incitement of some Israeli ministers."

Abbas seemed to be conflating the mass killings with an ongoing controversy over access to a Muslim holy site. Netanyahu has been clear that he will not alter the status quo at the site, which does not allow non-Muslim worship. But the issue has been used as a pretext for a recent spate of violence that has included knife and vehicular attacks against Israeli citizens.

Abbas and other Palestinian leaders should not try to equalize, equivocate or incite. The synagogue killings were immoral and illegal — period.

And Abbas should be unquestionably clear that further deaths may also claim the peace process necessary to achieve the legitimate goal of an independent Palestinian state. A two-state solution is still the official objective of the Israeli government, as well as the Obama administration. But brutality like Tuesday's attack only makes that goal more elusive.

Palestine should act like the state it aspires to be. Its leaders should forsake violence, and Fatah should reconsider its rapprochement with Hamas, which Israel, the United States, the European Union and several other responsible nations justifiably consider a terrorist organization. Those who question that assessment should read the Facebook post of Mushir al-Masri, a Hamas spokesman: "The new operation is heroic and a natural reaction to Zionist criminality against our people and our holy places. We have the full right to revenge for the blood of our martyrs in all possible means." Perhaps inspired by such cynicism, some Palestinians celebrated in the streets.

Abbas is trying to gain greater global recognition of Palestine in international organizations and from other nations. On Oct. 30, Sweden became the 135th country to recognize Palestine. And on Tuesday, the same day of the attack, the Spanish Parliament unanimously passed a nonbinding motion to ask the prime minister to do so. Every government that has recognized Palestine should now recognize its responsibility to pressure Abbas to combat extremism.

U.S. Secretary of State John Kerry was diplomatic, but blunt, in his response to the killings.

"So the Palestinian leadership must condemn this and they must begin to take serious steps to restrain any kind of incitement that comes from their language, from other people's language, and exhibit the kind of leadership that is necessary to put this region on a different path," Kerry said. "Our hearts go out to all Israelis for the atrocity of this event and for all the reminders of history that come with it."

Our hearts go out, too — for the victims and their loved ones, as well as for the cause of peace that is sabotaged by such violence.