The dead all belonged to the militant Sunni Muslim group Sipah-e-Sahaba, or Guardians of the Friends of the Prophet. They were attacked in a graveyard in Sikunder Pur, in northwest Pakistan, when the shooting occurred. They were there to bury a Sipah-e-Sahaba leader.
The gunman was identified by police as Salamat Shah, a Shiite Muslim, the Associated Press reported. Police reportedly said Shah attacked the funeral party because he did not want to remove a small building that local residents thought might become a Shiite Muslim mosque.
The Sunni-dominated local administration had ordered Shah to remove his building.
"We warned the administration that we feared he would try to attack us but they didn't do anything," said Hafiz-ur-Rehman, a local Sunni leader.
He said his organization, which has been blamed for the deaths of hundreds of Shiite Muslims in Pakistan, would hold a meeting to determine its response to the killing.
Most of Pakistan's 140 million people are Sunni Muslims. In recent years militant groups belonging to both sects have sprung up in Pakistan and often clash.