The assassination of Hezbollah leader Imad Mugniyah last week in Syria risks setting off considerably more trouble in the Middle East and potentially elsewhere.

It is important to say that, except perhaps from the standpoint of grieving family members, Mr. Mugniyah's departure from this world makes it a better place. In the 1980s and 1990s he was involved in a long list of evil deeds in the Middle East largely directed against the United States, Israel and the general peace. There was some poetic justice in the fact that it was a car bomb that took him out last Tuesday.

The answer to the first post-assassination question, however, is the most troubling part of what occurred. That is, "Who killed Mugniyah?" In typical Middle East fashion there are at least four possible answers.

The first, the one seized upon by Hezbollah leader Hassan Nasrallah in a speech telecast at Mr. Mugniyah's funeral in Beirut, was the most obvious -- Israel. The second is also possible, and most relevant to Americans: the United States. At one point, due to the number and horrific quality of some of the attacks on American assets that Mr. Mugniyah had been involved in, the United States offered a $25 million reward for him, dead or alive.

A third possibility is that his assassination was part of intra-Hezbollah wrangling for power and influence. They do kill each other, too. A fourth is that the Syrians had grown tired of hosting Mr. Mugniyah, who was Lebanese, in Damascus, thus incurring the international and domestic criticism that comes with sheltering accused terrorists -- and eliminated him.

Who actually killed Imad Mugniyah is not just an obscure question for Middle East experts to ponder. The reason is that Hezbollah leader Nasrallah has pledged to take revenge for Mr. Mugniyah's death. Hez-bollah still holds at least two Israeli soldiers, the ones whom Israel went into South Lebanon unsuccessfully in 2006 to try to free. The killing in Damascus could put them in danger.

If the United States did it, there are at least three potential problems. The first is that Hezbollah might take revenge on America. The second is Syria would not take lightly the United States carrying out a high-profile assassination in its capital. The third is the possibility that Hezbollah would take revenge on Israel for an American-executed assassination.

If there is a bottom line to this, it is that the Middle East is a very dangerous place, a region where the United States would be very hard-pressed to understand matters well enough to intervene violently with any safety.