The beheaded body of a British doctor working for the International Committee of the Red Cross was discovered on a Pakistani roadside Sunday.
Pakistani police discovered the corpse of Khalil Dale wrapped in plastic with a note reading: "This is the body of Khalil who we have slaughtered for not paying a ransom amount."
It also said that a video of the moment when Dale's throat was slit would soon be released.
Doctors had said that his head had been severed with a sharp knife and that he had been killed around 12 hours prior to the discovery of the body.
Dale, a 60-year-old health program manager with the ICRC, was kidnapped this past January while on his way home from work with the Red Cross in the southwestern Pakistani city of Quetta. He was driving in a clearly marked ICRC vehicle when he was stopped and bundled into a car by his kidnappers.
The Pakistani Taliban has claimed responsibility for the attack.
Quetta is Pakistan's largest and poorest province bordering Iran and Afghanistan. The province is home to troubled tribal areas and both Baloch separatists and Islamist militants have a presence in the volatile region.
The British doctor was from Dumfries, Scotland and was also known as Ken. He had converted to Islam years ago and was an experienced aid worker who had offered his services with the ICRC in the war-affected countries of Afghanistan, Somalia, Sudan, and Iraq prior to his arrival in Pakistan.
"The ICRC condemns in the strongest possible terms this barbaric act. All of us at the ICRC and at the British Red Cross share the grief and outrage of Khali's family and friends," ICRC Director-General Yves Daccord said in a statement.
"Khalil was a trusted and very experienced Red Cross staff member who significantly contributed to the humanitarian cause," Daccord added.
British Prime Minister David Cameron also condemned the killing as "merciless."
"This was a shocking and merciless act, carried out by people with no respect for human life and the rule of law. Khalil Dale has dedicated many years of his life to helping some of the most vulnerable people in the world and my thoughts today are with his friends and family," Cameron said on Sunday.