Chattanooga - A 24-year-old from an "average Chattanooga family", according to a former classmate. A high school wrestler with a degree in engineering. A man who apparently wrote earlier this week that life is "short and bitter".Hours after Mohammod Youssuf Abdulazeez allegedly opened fire at two US military facilities in Tennessee on Thursday, killing four Marines, little has emerged that would explain why he might have erupted in deadly violence.The FBI raided the home of the 24-year-old Abdulazeez in a leafy Chattanooga suburb and vowed to use every means possible to "determine the cause or the reason why he carried out this attack."Abdulazeez, a naturalised US citizen from Kuwait, according to NBC News appears to have maintained a blog, according to the SITE Intelligence Group, which monitors extremist activity on social media.In a post written Monday, he said that "this life is short and bitter" and that Muslims should not let "the opportunity to submit to allah, pass you by."The blog also makes fleeting references to sacrifice and jihad, but a blurb released by SITE did not contain any overt evidence of radicalisation or threats.A woman who attended Red Bank High School with Abdulazeez said he was a quiet kid, but well-liked."He was friendly, funny, kind," Kagan Wagner told the Chattanooga Times Free Press. "I never would have thought it would be him."His father She added that their whole family seemed normal."They were your average Chattanooga family," Wagner said.A high school yearbook quote which appears to belong to Abdulazeez, cited by local media, reads: "My name causes national security alerts. What does yours do?"He was on the wrestling team in high school, and the Chattanooga Times Free Press said a video posted on YouTube of a 2009 ultimate fighting competition does indeed show Abdulazeez.Abdulazeez has been in trouble with the law recently. Local media published a mug shot of him after he was arrested for driving while under the influence in April.Gunman in #Chattanooga shooting ID'd as 24-year-old Mohammad Youssuf Abdulazeez: http://t.co/zJqquDm5fj pic.twitter.com/sRbkBUgeXK— The Hill (@thehill) July 17, 2015He graduated from the University of Tennessee at Chattanooga in 2012 with a degree in engineering, WRCB reported.His father, who shares his name, works for the city's public works department where he was appointed as a "special policeman."A Facebook page which appeared to belong to his mother, and which AFP could not independently verify showed a cheerful photo of Abdulazeez smiling at his graduation as he hugs an elderly woman while draped in flowers and a Palestinian keffiyeh.Another photo apparently shows him posing with his diploma in front of the US and Tennessee flags, while a third shows a cake with the words "Congratulations Mohammod Class of 2012."His mother is from Kuwait and his father is from the West Bank, according to the Facebook page.