LAHORE, Pakistan — An American doctor volunteering at a hospital in eastern Pakistan was shot to death on Monday in front of his wife and 3-year-old son in the latest attack on a follower of the minority Ahmadi faith at a time of rising intolerance across the country.

One of two men on a motorbike opened fire on the doctor, Mehdi Ali Qamar, 50, a cardiologist based in Ohio, as he entered a cemetery in Rabwah, a town in central Punjab Province that is the main center of the Ahmadi community in Pakistan, the police said.

Dr. Qamar had arrived in Pakistan two days earlier as a volunteer at a hospital in Rabwah that has been a target of an extremist hate campaign in recent months. His wife, sister-in-law and son were with him when the shooting occurred.

The gunman shot Dr. Qamar at least 10 times, and he died immediately, Inspector Rana Anwar, the Rabwah police chief, said in a phone interview. The doctor’s relatives were not injured, the authorities said, and the attackers fled.