Police identified the attacker as Alaa Hisham Abu Dheim, 25, of the Jabal al-Mukabber district of East Jerusalem, which means he was carrying the "blue" Jerusalem identification card that made it easy for him to reach the seminary.

The gunman killed eight Jewish students and injured nearly a dozen others before security forces shot him dead. It was the first major attack in Jerusalem in nearly four years.

Reports from Jerusalem said Abu Dheim had previously worked as a driver for the religious school that he stormed on Thursday night. His family said the police later raided his family home in East Jerusalem and arrested nine of his relatives, and later released five.

Abu Dheim's relatives said he was a religious Muslim, that he had left his home at 7 pm Thursday after praying, and never returned. None of them said to which faction, if any, he was affiliated; and eyewitnesses said that the flags of Hamas, Islamic Jihad and Lebanon's Hezbollah were hanging outside his family house.

News agencies reported on Friday that Hamas's military wing, the Izziddine al-Qassam Brigades, claimed responsibility for the attack.

However, the militant group said it could not verify its responsibility. Its spokesman, identified as Abu Obaida, told the Qatar-based al-Jazeera news channel that the group would issue an official statement claiming responsibility if it were responsible. He blessed the attack as a "swift and natural reaction to the Israeli crimes and massacres in Gaza, whose shrapnel reached Jerusalem."

But on Thursday night, Lebanon's al-Manar TV claimed those responsible for the shooting were members of a previously unknown group calling itself the "Brigades of Free Men of Galilee – Group of the Martyr Imad Mughnieh and Martyrs of Gaza."

Imad Mughnieh was a top Hezbollah military commander who was killed in a car bomb in Damascus last month, for which the Shiite organization blamed Israel and vowed to avenge his assassination.

The attack on the seminary also came after more than 130 Palestinians – civilians and militants – have been killed in the Hamas-controlled Gaza Strip during an Israeli military operation. Two Israeli soldiers and one civilian were also killed during that assault.

Unconfirmed Israeli media reports said the authorities believe that Hezbollah may be the most likely party to have been behind the shooting attack, while sources in Beirut said that Israeli fighter jets flew over Beirut on Friday, which might be linked to Israel's suspicion of Hezbollah's involvement.

Israeli talking heads said Thursday's attack was different than previous ones carried out by Palestinian factions in Israel, which usually resorted to suicide bombings rather than opening fire with machine guns. This difference, they say, is an indication that a non-Palestinian group is responsible, strongly speculating Hezbollah, believed to be the Arab world's largest, strongest and best-equipped anti-Israeli group.

Hezbollah's Shiite spiritual leader Muhammad Hussein Fadlallah hailed the attack, saying in a Friday sermon that the "heroic operation in Jerusalem proved that the mujahedin in Palestine are able to hit the Zionists hard.

He added that it was a "natural reaction to the barbaric Israeli violence in Gaza," echoing similar remarks by Palestinian faction leaders and Arab commentators that the attack was part of an ongoing war between Israel, the Palestinians and other anti-Israeli groups such as Hezbollah.

Commentators in the Arab media criticized the quick Western condemnation of the shooting and the U.N. Security Council's convening of an emergency session to condemn the attack, while the international community failed to condemn the Israeli assaults that have killed dozens of Palestinian civilians.

Nevertheless, the Security Council resolution was blocked by member Libya because the draft did not condemn the Israeli killing of Palestinian civilians in previous days.

Palestinian Authority President Mahmoud Abbas himself denounced the attack, saying he condemns "all attacks against civilians, be they Palestinian or Israeli."

Analysts predicted that although the Israeli government has stressed it would pursue the paralyzed peace negotiations with Abbas' Fatah-led PA, it would retaliate militarily if it confirms that the attacker did not act alone.

They say his identity as a Jerusalem resident – and thus an Israeli citizen in Israeli terms – makes it difficult to pinpoint which Arab group had recruited him and supplied him with an assault rifle, and how to respond.

Some Arab and Israeli pundits said that if the attack did not turn out to be an isolated shooting spree, they expect an Israeli military escalation against Palestinian militants in Gaza and the West Bank, and possibly against Hezbollah in Lebanon, expanding the cycle of violence in the Middle East and making Israeli security – let alone the chances for peace – more vulnerable.