Wissam al-Hassan, a top Lebanese security official who worked closely under Rafik al-Hariri, Lebanon's former prime minister, was killed in a Beirut car bombing on Friday.
Prior to his death, the 47-year-old general had suspected the leadership in neighbouring Syria of orchestrating the assassination of his mentor al-Hariri in 2005.
As intelligence chief of Lebanon's police, the Internal Security Forces (ISF), Hassan dismantled networks of armed religious movements in his country and shut down Israeli-linked spy operations.
He was also instrumental in the ongoing investigation against Michel Samaha, former Lebanese information minister.
The investigation led to the August 9 arrest of Samaha over allegations that he was plotting to plant explosives in the northern city of Akkar at the behest of Ali Mamlouk, a Syrian intelligence official.
Hassan had previously pointed the finger at Damascus, not only for the Hariri assassination, but also for a series of killings of Lebanese figures opposed to Syria over the following three years.
Under his watch, the ISF was deeply involved in seeking the arrest of those responsible.
"They targeted General al-Hassan because he arrested Michel Samaha and he was a security official who feared nothing," said opposition politician Samir Geagea.
Omran al-Zohbi, Syrian information minister, condemned what he called the "terrorist, cowardly" attack.
|Hassan and two others were killed by a car bomb in the Ashrafiyeh neighbourhood on October 19 [Reuters]
Born in northern Lebanon's Koura region, Hassan entered the police academy in 1983.
Later responsible for protocol, he was often at Hariri's side.
After Hariri's death, Hassan took on the position he held until his own murder on Friday.
ISF officers described him as "the man for difficult jobs" but also one in the shadows.
When he died, he was travelling in an unmarked car without a convoy.
The killers, says a government official, must have known this because they attacked him in an alley with a car bomb that waited for him to pass.
According to Geagea, himself a target for assassination last April, "General Hassan alerted us every time to the threats against" members of the opposition hostile to Damascus.
Asked whether Syria was behind the attack on Hassan, he replied: "Who else could it be?"