It was 1983, and Mossad agent Eliezer Tsafrir stood on a Beirut rooftop observing Imad Mughniyeh's handiwork: two rising mushrooms of smoke and wailing ambulances racing to collapsed buildings where nearly 300 American and French troops had just been killed. Tsafrir, then Beirut station chief for the Israeli spy agency, was in a unique position to observe the rise of the Lebanese terror mastermind. In an Associated Press interview, Tsafrir offered an insider's take on Mughniyeh's mysterious assassination last week, saying it would have required years of patient intelligence work by dozens of operatives. Mughniyeh's organization, Hizbullah, and its Iranian backers immediately blamed Israel for the explosion that ripped through his Pajero SUV in the Syrian capital. Israel immediately issued an official denial of involvement, though some military officials' subsequent denials were less emphatic. Now 74, a grandfather in sneakers and a sweat shirt, Tsafrir retired in 1992 after an intelligence career that included stints heading Mossad operations in Kurdistan and Tehran. His memoirs have been published in Hebrew, Kurdish and Farsi. At his small apartment in a leafy Tel Aviv suburb, decorated with photos and other mementos from his years of service, Tsafrir looked back on Mughniyeh's career and his violent demise. The string of attacks attributed to Mughniyeh in the past quarter century includes blowing up U.S. and French buildings in Lebanon, airplane hijackings, attacks on Israel's embassy and a Jewish community center in Argentina and other attacks in Europe and the Arab world. He had been in hiding for years and reportedly had undergone plastic surgery to avoid being found. The Mossad's agents in Beirut became aware of the young Mughniyeh in the early 1980s, after Israel invaded Lebanon to evict Palestinian militants who had taken over swaths of the country, Tsafrir said. The Mossad was active alongside the military, and Tsafrir was in close contact with Lebanese Christian leaders allied with Israel. Mughniyeh, a Shiite Muslim from south Lebanon, had first signed up to fight with Yasser Arafat's Palestinian forces and then became one of the founders of a small pro-Iranian faction of local Shiites. "We started hearing his name at that time," he said. That group would eventually morph into the formidable Hezbollah organization, and Mughniyeh would become the group's operations officer and one of the world's most wanted terrorists. For Tsafrir, Mughniyeh's attacks had a personal aspect: His brother, an Israeli military officer, barely survived a 1983 car bomb attack on the Israeli army's headquarters in the Lebanese city of Tyre, and his son, commander of a tank company, was only steps away from another Mughniyeh-planned car bomb targeting an Israeli convoy in south Lebanon four years later. The Israeli agents in Lebanon were shocked by Mughniyeh's tactics, Tsafrir remembered. Suicide bombing, unknown at the time, would later be picked up by Palestinian militants in the 1990s, then elsewhere in the Islamic world before reaching a horrifying climax with al-Qaida's Sept. 11, 2001 attacks in the U.S. "We asked ourselves, 'How can this be?"' Tsafrir said. "We concluded that the Shiites, as an extreme sect, were more likely to do things of this kind. We asked ourselves if it was possible the Palestinians would follow their lead, but thought there was no chance because the Palestinians were Sunnis and more moderate." "We were wrong," Tsafrir said. In 1986, Ron Arad, an Israeli air force navigator, was shot down over Lebanon and taken captive by Shiite militants. Arad changed hands several times before disappearing without a trace, and "at each stage the name Mughniyeh popped up again," Tsafrir said. Arad's whereabouts remain a mystery today. Mughniyeh remained alive when Tsafrir left Lebanon in 1984 for other postings, and his assassination would wait more than two decades. Though Israel and the U.S. perhaps top the list of suspects, Tsafrir said, countries like France, Germany, and Saudi Arabia also had "unsettled accounts" with him, along with any internal opponents he might have had. "A person like this makes a lot of enemies," Tsafrir said. An operation like the one that killed Mughniyeh last week would have been tremendously complex, requiring years of intelligence work, months of planning, and dozens of people, he said. "It's not a matter of just pressing the button," he said. "An operation like this would take tremendous amounts of intelligence _ human intelligence, not electronic intelligence," he said. "You need the ability to find people, to check the location, to install the device, and to escape," no simple task in the middle of a hostile capital. "The agents could be recruited, or infiltrated into the organization, or both. But there would be dozens involved, and everything would be compartmentalized: people wouldn't know what the others were doing, and would only know what they needed to know," Tsafrir said. Mughniyeh's assassination has generated swirls of speculation about who killed him and how. Some anti-Syrian politicians in Lebanon have accused Damascus of being behind the killing. The U.S. intelligence chief, Mike McConnell, has suggested internal factions in Hezbollah or the Syria regime may be to blame. Reports in the Arab press have suggested Palestinians might have been involved. Hezbollah declined to comment on the U.S. claim. The Syrians have said they are investigating and will announce the results when the inquiry ends. Asked what the Mossad's policy is toward targets like Mughniyeh, Tsafrir would only give an example from the past: In 1972, after Palestinians from the Black September group killed 11 Israeli athletes at the Munich Olympics, Israeli Prime Minister Golda Meir gave an order to kill those who were responsible for the Munich bloodshed or planning new attacks. Over the next 10 years, Palestinian operatives were killed in cities across Europe in attacks widely attributed to Israeli agents.