Working theory

Powerline's "Trunk", in the course of trying to tar Hillary Clinton with the Syrian brush, notes this Israeli news item about the assassination of Imad Mughniyeh; note that the Israeli report is itself sourced to newspapers in Kuwait, but let's do what "Trunk" is trying to do and take it at face value --

A Kuwaiti newspaper reports that Hizbullah terrorist chief Imad Mughniyeh, who was killed in a car-bomb attack in Damascus on Tuesday, was in the midst of planning major terrorist attacks in moderate Arab countries when he was killed.

Al-Watan reports that American intelligence had learned that Mughniyeh arrived in Damascus three days earlier with instructions from, and in coordination with, the Iranians. His objective was to meet with Hizbullah leaders and coordinate a mass attack, for which he was to receive help from Syrian intelligence.

Another Kuwaiti newspaper, Al-Siasa, reports that Mughniyeh took part, shortly before he was killed, in a secret meeting in the Iranian School in Damascus. Also participating in the meeting were Syrian Intelligence Chief Gen. Aisaf Shwackath, Hamas chief Khaled Mashaal, and an Islamic Jihad representative.

So he was in a "secret" meeting that it seems only Syrian and Iranian intelligence knew about, and right afterwards he was dead. If this incident was being investigated by actual police, it's obvious where their suspect list would start. The last people who saw the deceased alive.