CIA-trained assassins?

Youssef and Shukoor have the clearest report on the recent controversy surrounding US-backed Afghan troops' egregious behaviour:

Afghans blame U.S.-led coalition for police chief's killing
By Nancy A. Youssef and Hashim Shukoor - McClatchy Newspapers

KABUL, Afghanistan, June 29 — The Afghan government Monday blamed U.S.-led coalition forces for the killing of Kandahar's police chief and criminal investigations director on coalition forces, saying the Afghan guards that shot them to death were working for and trained by the coalition...

American intelligence agencies are investigating whether some of the guards may have been among the Afghans whom the CIA has recruited, trained and paid to help fight the Taliban, al Qaida and drug trafficking.

Coalition officials in Afghanistan said only that no U.S. or coalition forces were involved in the killings, that the guards weren't acting "on behalf of U.S. or international forces" and that the killings in Kandahar, Afghanistan's second-largest city and the heart of its opium poppy-growing region, were an "Afghan-on-Afghan" incident...The shooting began sometime after 11 a.m., when about a dozen vehicles carrying some 40 Afghan guards pulled up to the prosecutor's office. The guards, whom Kandahar officials charge work with American Special Forces on counter terrorism raids, accosted the prosecutor, threatened him and demanded the release of a fellow guard named Assadullah...

The prosecutor refused and called the provincial police chief, Matiullah Qati, who arrived with four police officers who serve as his guards and Abdul Khaliq, the province's criminal investigations director.

A dispute arose, and the guards began shooting at Qati and Khaliq, according to Ahmed Wali Karzai. The shooting lasted for about 10 minutes, Karzai said, and left Qati, his four police guards and Khaliq dead. Another six officers were injured. It was unclear whether any of the guards were killed.

Local police arrested at least 41 guards afterward... (link)

The BBC has an intriguing take on the legal status of these mysterious security forces:

Afghan guards are often employed at coalition military bases across the country.

They are paid and trained by the US. While the guards are recognised by the Afghan government, they do not come under their command.

Locals often refer to these guards as Afghan special forces as they are well-trained and well-armed, our correspondent says... (link)

This description of the Afghan special forces seems roughly to correspond with descriptions of the forces which carried out the Toube massacre - which, to my knowledge, has only been covered in English by this blogger, the Telegraph (UK), and the Insitute for War and Peace Reporting. In Toube, Afghan and foreign special forces were said to have helicoptered into the village late at night and killed families in their homes.