A former lawyer for the doctor who helped the CIA look for Osama bin Laden has been shot dead in northwest Pakistan, police said. Unidentified gunmen attacked the lawyer, Samiullah Afridi, in his car near the city of Peshawar on Tuesday, said Mian Saeed, a police superintendent in Peshawar. Two different militant groups claimed responsibility for the killing. The lawyer had represented Dr. Shakeel Afridi, who was convicted of treason in 2012 by a Pakistani tribal court and is now serving a 23-year prison sentence. The two men are not related. The doctor helped the CIA set up a fake vaccination campaign in an attempt to collect DNA samples from relatives of Bin Laden in an effort to verify his presence in a compound in the Pakistani city of Abbottabad. The Qaeda leader was killed in a U.S. raid on the compound in May 2011. It was unclear which of the two groups claiming responsibility for the attack was actually behind it. Fahad Marwat, a spokesman for the militant group Jundallah, told CNN that Afridi was on the group's hit list. But Ehsanullah Ehsan, a spokesman for a faction of the Pakistani Taliban, said his group had carried out the assassination because Samiullah Afridi defended the doctor, whom he described as "a friend" of bin Laden's killers. CNN national security analyst Peter Bergen said Jundallah is "kind of a splinter group" of the Pakistani Taliban that's "been around for a long time." "They're extremely violent," he said. "They've been killing all sorts of religious minorities in Pakistan." Last month, the group claimed responsibility for a suicide bombing outside a Shiite mosque in the city of Rawalpindi.