Shocking. Horrifying. And, of course, it begs the question, "What now?"
Obviously, it's too early to pick a perpetrator. However, the strongest suspects are the Sunni militant groups, the Spah-e-Sahaba, or its rival splinter organization, Lashkar-i-Jangvi. Both are responsible for widespread terrorism in Pakistan, from attacks on minority Shi'ites to the assassination of journalist Daniel Pearl. Both believe the same as their Taliban and Al Qaeda allies, that the only legitimate government of Pakistan would be an Islamist state.
Benazir Bhutto, therefore, sits at the pinnacle of things that offend them. She is running for election, when these groups want elections to end. She is willing to work with the United States and Europe. And, of course, she is a woman.
However, Bhutto isn't the only target. On the same day, a sniper fired on Nawaz Sharif. The same group may be responsible for both assassination attempts; the group or groups responsible may be Spah-e-Sahaba and Lashkar-i-Jangvi. We don't know yet.
That uncertainty, however, adds fuel to the already incendiary politics of Pakistan. Suspicion will also fall on Musharraf, particularly since it's likely that he will tighten police and military control, and possibly suspend the elections. The fact that Musharraf has also been the regular target of assassination attempts may be lost in the outrage over Bhutto's death.
The assassination occurs at a bad time for US officials. Already, high-ranking diplomats and military officers were quoted in a series of New York Times articles detailing the problems with the US alliance with the Pakistani government. Pakistani security forces aren't vigorously fighting the Taliban and Al Qaeda cells within their borders, leading to the conclusion that billions of dollars of military aid were largely wasted.
The Administration is clearly putting some daylight between itself and Musharraf; now, with Bhutto's assassination, it will be more difficult to pressure him, the Pakistani military, or the intelligence services.
The worst consequence of Bhutto's assassination is heightened fear and anxiety. Militant Islamists aren't confined to the distant "tribal areas;" instead, they're able to kill even one of the best-protected leaders, in one of the most heavily-policed cities.