A lone assailant armed with grenades and a pistol attacked a religious gathering in northwestern Pakistan, killing at least one person, fatally wounding himself and injuring 18 others, police said Friday. The attacker, a Pakistani, was wounded while hurling a grenade just before midnight Thursday in the city of Bannu and died later at a hospital, said Bannu's police chief, Dar Ali Khan. The attack took place at the regional headquarters of a group of Muslim preachers who were holding a gathering. The motive for the attack remained unclear and police were investigating, Khan said. He said hundreds of people had been praying or listening to lectures from senior clerics at the time.