The Saudi Air Force trainee who killed three sailors at a U.S. Navy training center in Florida last week had previously filed a complaint against one of his instructors for ridiculing him with the nickname “Porn Stash,” The New York Times reports. The gunman has been identified as Second Lt. Mohammed Alshamrani, who was a visiting Saudi student at the Pensacola Naval Air Station. Earlier this year, he reportedly filed an official complaint against one of his instructors, who left him angered in class by giving him the derogatory nickname. “I was infuriated as to why he would say that in front of the class,” the Saudi trainee reportedly wrote. Investigators are still searching for a motive for the Friday morning attack, and there has been no suggestion that the April incident led to the shooting. The instructor reportedly asked Lt. Alshamrani if he had any questions, repeatedly addressing him as “Porn Stash,” but the trainee didn’t respond.