JERUSALEM, Dec. 18 (JTA) — Palestinian security forces have arrested the third member of a terrorist cell responsible for last week’s attack in which an Israeli mother and her son were killed. The two weapons used in the Dec. 11 attack near the West Bank settlement of Beit El were found in the possession of the third suspect, a member of a cell of the Damascus-based Popular Front for the Liberation of Palestine, which militantly opposes the peace process. The two other suspected terrorists were arrested by Palestinian security forces the night of the attack. After carrying out the attack, which killed Ita Tzur, 42, and her son, Ephraim, 12, the terrorists fled to the nearby town of Ramallah, which is under Palestinian self-rule. In a crackdown on the PFLP cell in the Ramallah area, Palestinian Authority security forces arrested dozens of other Palestinians, some of whom were suspected of having aided the terrorists. Word of the latest arrest came as settlers in Beit El laid the cornerstone Wednesday for a new neighborhood that will be built in the settlement in memory of Ita and Ephraim Tzur. The Israeli government has not approved construction at the site. Yoel Tzur, who was wounded in the attack along with his four daughters, had a mixed reaction to the arrests. “Certainly I’m glad they were captured,” he told Israel Radio. “But we all know that this is where it stops. They will be tried [by the Palestinian Authority], never handed over to Israel, and we will not hear any more about it.” Under the terms of the Israeli-Palestinian accords, Israel can request the extradition of suspected terrorists, but the Palestinian response can be delayed if the suspects are serving prison terms in the self-rule areas. Earlier this week, Jibril Rajoub, who is in charge of all Palestinian security forces in the West Bank, said that the suspects would not be handed over to Israel, as it had requested, but would be tried and sentenced in the autonomous areas. Israel Radio reported that the terrorists who carried out the attack were acting under orders from the PFLP leadership in Damascus, which funds the group and is considered more extreme than the group’s leadership in the territories. Meanwhile, Palestinian police in the Gaza Strip briefly blocked the road to Netzarim to protest Israel Defense Force work on an observation post near the Jewish settlement. The road was reopened after the police were convinced that the repair work was routine.