CHATTANOOGA • Hours before the Tennessee shooting that killed five US servicemen, the suspected gunman texted a close friend a link to an Islamic verse that included the line: "Whosoever shows enmity to a friend of Mine, then I have declared war against him."
The gunman's family said in a statement late on Saturday that he had suffered from depression, and that they had experienced shock and horror over the violence.
The suspect's friend said he thought nothing of the text message at the time, but now wonders if it was a clue to Thursday's rampage in Chattanooga, which has reignited concerns about the radicalisation of young Muslim men.
"I didn't see it as a hint at the time, but it may have been his way of telling me something," the friend said on Saturday, requesting anonymity for fear of a backlash.
The suspect, Mohammod Youssuf Abdulazeez, a Kuwaiti-born naturalised US citizen, was killed in a gunfight with police.
The Federal Bureau of Investigation (FBI) is investigating the attack as an act of terrorism, but said it was premature to speculate on the gunman's motive.
Abdulazeez's family offered condolences to the families of the "victims of the shooting our son committed on Thursday".
"There are no words to describe our shock, horror and grief," they said in a statement.
"The person who committed this horrible crime was not the son we knew and loved," they said, adding that "for many years, our son suffered from depression" and "his pain found its expression in this heinous act".
While a firm connection between the 24-year-old suspect and radical Islam has not been established, the shooting follows a series of attacks or thwarted attacks in the United States and other countries by Muslims claiming to be inspired by the Islamic State in Iraq and Syria (ISIS) or other militant groups.
Abdulazeez returned from a trip to Jordan last year concerned about conflicts in the Middle East and the reluctance of the US and other countries to intervene, according to two friends who knew him since elementary school.
He later bought three assault rifles in an online marketplace and used them for target practice, they said. "That trip was eye-opening for him. He learnt a lot about the traditions and culture of the Middle East," said one of the two friends, the person who received the text message from Abdulazeez.
The night before the attack, just after 10pm, the friend received a text message from Abdulazeez with a link to a hadith, or Islamic teaching: http://sunnah.com/ nawawi40/38. He showed Reuters the text message on his phone.
Abdulazeez's friends said he occasionally smoked marijuana and drank alcohol, and struggled to reconcile that with his faith in Islam.
The first friend said tensions between Abdulazeez and his Palestinian parents had also upset him. His parents nearly got divorced in 2009, according to court records.
The friend said Abdulazeez had a well-paid job and had many plans for his life, including possibly starting a computer sales business in Chattanooga.
"He wanted to buy a car. He wanted a video console, to make a man cave - every guy's dream."
He said it was difficult to understand how his friend became the suspect in the rampage. "The signs just weren't there," he said.