Pat Tillman’s father called Army investigations into his son’s death “shams” in a letter to The Washington Post on Saturday, and accused investigators of deliberately falsifying facts to cover up Army mistakes.

The letter, which offers clarifications to comments Pat Tillman Sr. made to The Washington Post on May 23, said that calling him “critical” of the Army’s handling of the investigation is an understatement.

“I did not say the Army ‘botched’ the investigation,” the letter read. “I said it deliberately falsified baseline facts — e.g. distance, light conditions, details perceived before and while firing, and the identification of ‘friendlies.’”

Tillman, a former Arizona Cardinals safety, was killed in a friendly fire accident in Afghanistan on April 4, 2004.

The letter in The Washington Post accuses Army superiors of ordering that all physical evidence of the friendly fire incident be destroyed, including Tillman’s uniform and body armor. Tillman Sr. also wrote that his family was briefed three times with “a sales pitch of made-up ‘facts’ and assurances of investigative integrity.”

Tillman Sr. wrote the initial reports of his son’s death — which the Army later said were mistakes — were actually “deliberate, calculated, ordered repeatedly and disgraceful — conduct well beneath the standard to which every soldier in the field is held.”