The IDF had received a green light to respond harshly to the bomb attack, though defense officials would not provide details on the planned response, but said it would be in line with Israel's new policy to respond aggressively to any attack following the end of Operation Cast Lead earlier this month. A Beduin tracker was killed and an officer was seriously wounded when a large bomb exploded next to their patrol along the border near the Kissufim Crossing. Two other soldiers were lightly wounded. The bombing was the first lethal attack by the Palestinians since Israel withdrew from Gaza last week. The family of the fatality requested that neither his name nor his photo be published. Following the incident, the IDF fired at several targets inside Gaza, and soldiers briefly crossed the border in search of the attackers. The troops left Gaza by nightfall after discovering several additional explosive devices that had been planted nearby. IDF sources said the terrorists had likely taken advantage of the heavy fog Tuesday morning to plant and detonate the device. Defense Minister Ehud Barak called an urgent meeting of top defense officials after the bombing. "This is a serious attack, and we will respond, but there is no point in elaborating," Barak said. Israel closed its Gaza border crossings to humanitarian aid traffic after briefly opening them Tuesday morning. Gaza border official Raed Fattouh said Israeli officials had informed him the closure was due to the attack. Amos Gilad, head of the Defense Ministry's Diplomatic-Security Bureau, said Israel's response would not be limited to closing the crossings into Gaza. "The response will not be the way it used to be," Gilad said in a speech at the Institute for National Security Studies in Tel Aviv. "The equation has changed." In the afternoon, a helicopter gunship struck a motorbike in Khan Yunis that was reportedly carrying a Hamas operative involved in the attack. The IDF said it was possible that the bombing had not been carried out directly by Hamas, but by other Palestinian terror groups. IAF helicopters hovered in the air firing machine gun bursts, Palestinian witnesses said. An IAF jet set off a loud sonic boom over Gaza City not long afterward, possibly as a warning. Palestinians reported that several people were wounded when IDF tank shells hit residential buildings in the Strip. Not long after the bombing, a 27-year-old Gaza farmer was killed by Israeli gunfire along the border several kilometers away, according to Dr. Moaiya Hassanain of Gaza's Health Ministry. Two other Palestinians were wounded. The army had no comment, and it was unclear whether the two incidents were related. There was no claim of responsibility for the attack, but Hamas leader Mushir al-Masri said Israel was to blame for continuing to fire into Gaza. Masri said his group had not agreed to a full cease-fire but only to a "lull" in fighting. "The Zionists are responsible for any aggression," he said. Meanwhile, Foreign Minister Tzipi Livni told a gathering of the New York-based World Jewish Congress in Jerusalem on Tuesday that Israel would no longer show restraint against Palestinian attacks from the Gaza Strip. "Israel is going to act according to a new equation. We are not going to show restraint anymore," Livni said. "We need to change the rules of the game until they learn that the rules have changed and the equation has changed." Livni added that Israel needed to negotiate with the Fatah leadership in the West Bank toward a two-state solution, while continuing to fight against Hamas in Gaza. "For me, an agreement with Hamas is not an option," she declared.