Three American doctors were shot dead Thursday at a hospital in Kabul by an Afghan security guard hired to protect them.
The guard opened fire on American pediatrician Jerry Umanos and two U.S. visitors, a father and son, killing the three men and wounding a nurse.
The suspect, a member of the Afghan Police Protection Force, reportedly shot himself and is in custody.
"The wounded have been taken to the hospital and the attackers also apprehended by the police. So we are currently investigating to find out about the motives of this attack," Afghan Interior Ministry spokesman Seddiq Seddiq said.
District Police Chief Hafiz Khan said the security guard's motive is yet unknown.
The attack took place at Cure International Hospital, part of a Christian network of charitable hospitals and surgical programs, whose motto is "curing the sick and proclaiming the kingdom of God."
Dr. Umanos had been working to help the people of Afghanistan for the last seven years through the Christian charity, Cure International. He had been on staff at Lawndale Christian Health Center in Chicago for over 25 years.
"This loss is a great loss for his family, for those of us he worked with as well as for the people of Afghanistan. He was a loving, caring physician who served all his patients with the utmost of respect," Dr. Bruce Rowell, chief clinical officer of the health center, said.
The unidentified nurse is reportedly in stable condition.
In a statement Thursday, Cure said it "remains committed to serve the people of Afghanistan."
The attack is the latest in a series of deadly violence against foreigners in Afghanistan.