An Afghan policeman shot dead three foreign staff at a police training center in Herat Province on July 22.
Afghan security and intelligence officials say the gunman also injured the trainers' Afghan translator.
The attacker reportedly worked for the regional police command.
He was killed later in a shoot-out with troops from the NATO-led International Security Assistance Force.
An ISAF statement said the three foreign staff were civilian contractors working for NATO as trainers.
Meanwhile, officials say an Afghan army soldier opened fire on his NATO colleagues in northern Afghanistan on July 23, injuring two U.S. troops.
The deputy governor of Faryab Province, Abdul Satar Barez, said the Afghan soldier was killed when U.S. soldiers returned fire.
Killings of foreigners by Afghan government forces has escalated this year as Kabul recruits more Afghans to take over security ahead of NATO's planned withdrawal by the end of 2014.
A total of 29 foreign troops or civilian contractors have been killed by Afghan police or soldiers since the beginning of the year.
With reporting by AFP and the BBC