Afghan authorities said Sunday they are looking for an Afghan intelligence official they believe may be responsible for shooting dead two U.S. officers at close range Saturday inside a heavily guarded command center at the Interior Ministry in Kabul.

Officials have identified the shooter as Abdul Saboor, a 25-year-old intelligence officer, who had studied in Pakistan.

The killing of the U.S. officers, a lieutenant colonel and a major, took place as Afghanistan was in the fifth straight day of protests across the country following the burning of Qurans by NATO personnel at Bagram Air Base on Tuesday. Dozens of people have died in the demonstrations.

Afghan President Hamid Karzai called for calm Sunday in a televised address. He said “now that we have shown our feelings, it is time to be calm and peaceful.”

Despite the plea, protests continued. One protester was killed and seven American soldiers wounded when a grenade was lobbed at a U.S. base in Kunduz province in northern Afghanistan Sunday.

All international military personnel working in Afghan government offices were recalled Saturday after the gunman killed the two U.S. officers. NATO said the decision to order the recall came “for obvious force protection reasons.”

The Afghan Taliban has claimed responsibility for the ministry shooting, and said the attack was retaliation for the burning of the Muslim holy book.

U.S. President Barack Obama and other U.S. officials have apologized for the desecration of the Quran, but that has done little to quiet the outrage in Afghanistan and neighboring Pakistan.

NATO is conducting a full investigation of the incident, but has not issued a detailed statement yet. Media reports quoted unnamed Western officials as saying it appeared that the copies of the Quran in question and other Islamic readings in the library at Bagram were being used to fuel extremism, and that detainees were writing on the documents to exchange extremist messages.