Of all of the suicide attacks we've been unfortunate enough to learn about in recent years, when was the last time the attacker sniped his victims dead-on and then proceeded to kill him or herself? Benazir Bhutto didn't die because of a suicide attack, she was sniped by two bullets, one to the neck, and the other to the chest. My guess is that the aim of the blast that followed the shots was not to maximize casualties or to make extra sure that Bhutto died but to give the distinct impression that all of the deaths, including that of Bhutto, was a result of a suicide bomber. The failure of the bomber--whether he/she was a suicide attacker or whether he/she detonated the bomb via remote--was that he/she failed to destroy the evidence that Bhutto was killed by a sniper. In other words, the bomber failed in his mission to make the whole thing appear to be a massive suicide attack.
And why would they want to make it appear to be a suicide attack? To pin it on "the Islamists" and thus far away from Musharraf, who shared with Bhutto a distaste for them and thus could not be blamed for conspiring with them against her. For Musharraf (and perhaps his US-backers as well) the situation is a win-win: Musharraf's biggest challenger in the elections is eliminated, and he gets to condemn his other enemies, "the Islamists," for her violent death and justify more crackdowns on the people of Pakistan to boot.
When Benazir first returned to Pakistan, I made up a little jingle that will make sense only to Persian and perhaps Urdu speakers: Benazir may be be-nazir, but musharraf is bi-sharaf.
I was not a fan of Benazir. I know very well that she has been accused of ordering the assassination of her own brother, and everyone knows about the charges of financial corruption, but I think it was brave of her to return to Pakistan and refuse to make a power sharing deal with Musharraf. And her murder in Rawalpindi, in the same town where her father executed nearly thirty years earlier, will make her an icon, if she wasn't one already.