A note found with the body of Dr. Khalil Ahmed Dale, 60, said the Yemen-born British national was killed because the International Committee of the Red Cross had failed to meet the kidnappers' ransom demand.
"The body bore multiple bullet wounds and marks of tortures," doctors at a Quetta hospital said Sunday.
The ICRC said in a written statement that Dale had been working as a healthcare program manager in Quetta for nearly a year. He had previously been stationed in Somalia, Afghanistan and Iraq.
"We are devastated," said Yves Daccord, director-general of the ICRC. "Khalil was a trusted and very experienced Red Cross staff member who significantly contributed to the humanitarian cause."
A Red Cross official told The Daily Express the organization would continue to operate in Pakistan even though it had scaled back its programs this year.