EXCLUSIVE: Inability to learn English, pay cut behind Afghan’s murder of 9 Americans at Kabul military base

The Afghan soldier who gunned down nine Americans in a shooting rampage at a military compound in Kabul last April targeted and killed his U.S. mentors after they took away his wings and cut his salary nearly in half because he was unable to learn English, a longtime colleague of the killer has told FoxNews.com.

A second Afghan airman, who was wounded in the April 27 attack, says the gunman, Col. Ahmed Gul, also intended to kill Afghans who were working with the Americans at the base at Kabul Airport. And he said he fears there will be more incidents like it as the war winds down.

A U.S. Air Force Special Investigation report on the attack that was released last week concluded that Gul, 46, acted alone, and it found no evidence that the attack was connected to the Taliban or insurgents. It noted reports of Gul’s mental and financial problems, but it did not mention Gul’s failure to learn English as a possible motive.

The Air Force report, said the Afghan official who was wounded in the shooting, also reveals clear evidence that the Ministry of Defense failed to conduct a proper background check on Gul, who had returned to active duty after spending 18 months in military housing in Hayatabad, Pakistan, where he became radicalized and increasingly anti-American.

According to the report, a relative of Gul said he started following the teachings of the Taliban in 1995, then later left Afghanistan for Pakistan because “he was upset that foreigners had invaded his country.” When asked why Gul returned to Afghanistan in 2008, he said he “wanted to kill Americans.”

Gul’s longtime colleague, who attended the Afghan Air Force Academy with him, said the gunman’s failure to learn English and qualify for the highly paid position of active-duty Level 1 pilot -- a position he held when Afghanistan was under Taliban rule -- was likely a significant motive behind his rampage. Gul was enrolled in mandatory English classes for all pilots in Kabul, but he was unable to complete the course successfully, the colleague told FoxNews.com.

Because Gul could not return to active duty as a Level 1 pilot, he was forced to take a non-flying job at nearly half the salary.

“Ahmed Gul was very, very angry because of this. He blamed the Americans and the mentors --the mentors working at that same office -- maybe I think he targeted them because of this,” the colleague said.

Gul, who had a gambling problem, was unable to support his six or seven children -- including two children attending college in Kabul -- and had to sell the family home to pay off his debts, the colleague said.

“He had a lot of financial difficulties, he was suffering from poverty, he was crazy because of the poverty,” said the airman, who served with Gul in the Afghan Air Force for 20 years.

“But he could not learn English. He wouldn’t learn English. He needed the bonus and he wanted to fly. He was very, very good pilot, the best. But now we must learn English and he could not. So he could not get bonus. He was very, very angry.”

When asked for comment on whether Gul’s failure to learn English might have been a motive in the attack, spokeswoman Linda Card of the U.S. Air Force Office of Special Investigations told FoxNews.com via email:

“We have none and have never had any of this information.”

A recently implemented NATO policy established a system of bonuses for Afghan pilots based on their classification level. Level 1 pilots, who are qualified to fly in any weather condition and at night, are the most elite airmen; Level 2 pilots fly in poor conditions but not at night; Level 3 pilots can fly only in clear conditions and during the day.

Prior to the Afghan civil war, pilots received bonuses based on their level of skill and classification. But when the Afghan Air Force was reconstituted, that bonus system was not reimplemented. This changed in 2009, according to Gul’s colleague, when the U.S. agreed to fund the airmen’s bonuses on the condition that the pilots learn English, the internationally recognized language for flight and air traffic control communications.

English-language training courses for Afghan pilots began in 2007, said David Smith, spokesman for U.S. Air Force, Air Education and Training Command. He could not confirm when the bonus system was established. Gul returned from Pakistan in 2008.

If Gul, who had been a top pilot in the Afghan Air Force, had learned English, he would have earned $600 a month as an active Level 1 pilot. Instead, he was given a job as a non-active pilot making approximately $350 a month, according to figures provided by an Afghan military official.

“This may have been the last thing to push him over edge -- he was very good pilot, but he could not learn English,” his colleague said. “They said he could not fly. He could not have bonus. I think this had big effect on him.

The colleague said it wasn’t fair to expect older pilots to become fluent in English. “It is impossible for over 45 years old, to learn English fluently,” he said. “Ahmed Gul wanted to be first-class pilot, but he didn’t speak English language. He had some disagreements with his mentors about this.”

Some of those mentors appear to be the U.S. soldiers Gul targeted and killed before taking his own life in April.

In response to requests for comment with U.S. military officials in the U.S. and in Afghanistan, Air Force spokesman Chris Isleib said:

"The best source of information on this incident is the investigation report. There is no mention of English classes, or other classes, in the official report. We are not able to speculate into the motives behind this tragedy."

Interviews with Gul’s relatives, which are included in the U.S. Air Force report, reveal that Gul’s radicalization was known -- at least to some -- and that warning signs were ignored, including phone calls from relatives of the shooter, including his brother, warning that he was not safe to return to active duty.

Nevertheless, Gul cleared a background check and returned to active duty in July 2010.

Nine months later, he found himself armed with two American pistols -- one registered to his name by the Air Force; the other unregistered -- in a room with top-level U.S. military. He killed eight U.S. airmen and a civilian contractor.

The Afghan official wounded in the attack, meanwhile, says he believes he was personally targeted, and he said the U.S. investigators underestimate the threat to Afghan military who work closely with American forces. He said he expects there will be more attacks, and he said he fears for his life as U.S. and NATO troops plan their systematic withdrawal.

According to testimony included in the Air Force report, Gul yelled outside of the building, “Good Muslims please stay away or “Muslims don’t come close or you will be killed.”

“Maybe he said that outside, but he said nothing when shooting inside. He targeted me. He is against the U.S. and people like me working with the U.S,” the Afghan official said.

“We are not safe. I am not safe. Afghans working with the U.S., we need protection. There is corruption within Afghan government and Ministry of Defense. I am afraid for my life,” he said.