Recently released NSA documents confirmed what many had long suspected; that it was Israeli commandos who raided the seaside estate of a Syria general in 2008 and killed him. The commandos then left the way they came and no one took credit for the killing. But the Syrians knew who did it and why. The Israelis were sending a message in an ancient Middle Eastern way, by repaying an enemy for a past injury.
The dead man, Muhammad Suleiman, was a senior official in the Syrian government, in charge of things like nuclear weapons research. Suleiman was responsible for building the Syrian Al Kibar nuclear research facility Israeli warplanes destroyed in 2007 as well as several other very secret military and intelligence projects. Chief among these was supervising Syrian support for Hezbollah during the 2006 war between Hezbollah and Israel that left 165 Israeli dead.
Technically, Israel had no legal right to kill Suleiman but technically Suleiman and Syria had no right to develop nuclear weapons and support Hezbollah in firing thousands of rockets into northern Israel. Thus neither Israel nor Syria publicized the death of Suleiman, the Syrian nuclear research effort or Syrian support for Hezbollah. Both countries know that all this stuff is how diplomacy is conducted in the Middle East.