Gunmen ambushed and killed the lead Pakistani prosecutor investigating the 2007 assassination of former Prime Minister Benazir Bhutto on Friday, spraying his car with bullets as he drove from his home in Islamabad to a hearing in the case. The prosecutor, Chaudhry Zulfikar Ali, was shot 13 times in the chest and shoulder, according to a doctor, and died after being taken to a hospital. Shortly before his death, Zulfikar had reported receiving death threats — although he didn't say from whom.

No group immediately claimed responsibility for the attack, and police said it was too early to speculate on the motive. There's no shortage of possible culprits, though. Zulfikar was working on several complex and high-profile cases, and it's widely assumed that his murder was linked to his work, which included not just the Bhutto case, but also the investigation of Islamist militants suspected in the deadly 2008 terror spree that left 166 people dead in India's commercial capital, Mumbai.

Zulfikar was killed as he headed to a bail hearing for former president and military chief Pervez Musharraf. Days before his death, Zulfikar told reporters he had "solid evidence" connecting Musharraf to Bhutto's death. Musharraf was in power at the time of the assassination, but he's now under house arrest after returning from a self-imposed exile in hopes of making a political comeback. The former leader denies accusations that he failed to provide Bhutto with adequate security, which a 2010 United Nations report said could have prevented the attack that killed her. Zulfikar initiated the move to arrest Musharraf, says M Ilyas Khan at BBC News, "an unprecedented move that reportedly angered some quarters in the military."

Timing isn't the only thing pointing to the possible involvement of Pakistan's security apparatus, Khan says. Zulfikar had also "pushed the court to expedite proceedings against five members of the Pakistani Taliban faction called the TTP, detained for Bhutto's murder." Taliban leaders denied involvement in the 2007 attack, but members of the militant Islamist group have been implicated recently in a string of assassinations targeting secular candidates ahead of May 11 general elections. The vote is seen as a crucial milestone for Pakistan — it would mark the first time that an elected government has served out its term and transferred power to another democratically elected crop of leaders — so any violence that adds to tensions ahead of the balloting casts suspicion on the Taliban.

Of course, the killing might have nothing to do with the Bhutto case. "As CNN notes," says Ed Morrissey at Hot Air, "it might be the same group that conducted the Mumbai attack, Lashkar-e-Taiba." Zulfikar was scheduled to appear in a hearing regarding that case on Saturday. Morrissey goes on:

The Pakistani intelligence service ISI has supported LeT in the past (as they have the Taliban), and they may have concerns that Pakistan's prosecutors might get too interested in bringing these terrorist groups to heel. In other words, this is a real whodunit, just as much as with Bhutto's assassination — and it's unlikely that we'll ever get answers in either. [Hot Air]

Regardless of where the investigation leads, it immediately added to already rising tensions as the election gets closer. Lawyers have walked off the job in protest. Musharraf's lawyers want him excused from making court appearances due to security concerns, and his hearing was pushed back to May 14. And whatever happens next, says Declan Walsh in The New York Times, the prosecutor's "death reinforced the vulnerability of senior government officials who challenge Islamist militants and other powerful interests" in nuclear-armed Pakistan.