CHATTANOOGA (Tennessee) • A United States Navy petty officer has died of wounds sustained in last week's shootings here, the US Navy said yesterday, raising the number of people killed in the attacks to five.
The suspected shooter, Mohammod Youssuf Abdulazeez, a Kuwaiti-born naturalised US citizen, died on Thursday in a firefight with police after the rampage at two military facilities.
The Navy's brief statement did not identify the petty officer who died or provide his age or hometown. Four US Marines were also killed in the attacks and two others, a Marine and a police officer, were wounded.
Reports about the fifth casualty came as federal investigators dug into the background and travels of the 24-year-old gunman, focusing on a seven-month trip he made last year to Jordan and scouring his electronic trail in search of a motive.
The crucial, unanswered question was whether Abdulazeez came into contact with, or was inspired by, any Islamist extremist groups, intelligence officials said last Friday.
Federal agents flew Abdulazeez's computer, cellphone and other electronics to Washington for forensic analysis of his communications.
They also worked with local law enforcement, following up on 70 leads about his activities, and they asked intelligence services in Jordan and Kuwait about his movements there.
Abdulazeez was the son of Palestinians from Jordan, and made several trips to Jordan and Kuwait, where he had relatives, officials said, but he spent most of his life in south-eastern Tennessee, and graduated from college here.
Said Mr Edward Reinhold, the agent in charge of the Knoxville office of the Federal Bureau of Investigation: "It would be premature to speculate on exactly why the shooter did what he did. However, we are conducting a thorough investigation to determine whether this person acted alone, was inspired or directed."
Officials said there was no indication so far of any links to terrorist groups, leaving them to wonder how a young man with no known history of violence or radicalism turned up last Thursday with several weapons, spraying bullets at Americans in uniform.
Some "lone wolf" attacks have been carried out by people who had no direct contact with extremist groups, but were influenced by messages online, like those from the Islamic State in Iraq and Syria urging Muslims to take up arms and attack US military sites.
"This attack raises several questions about whether he was directed by someone or whether there's enough propaganda out there to motivate him to do this," said a senior US intelligence official, who spoke on the condition of anonymity.
Just days before the attack, Abdulazeez began a blog where he posted about Islam, according to the SITE Intelligence Group, which tracks international terrorist groups. At one point he compared life to a prison and at another point called life "short and bitter".
Abdulazeez graduated in 2012 from the University of Tennessee at Chattanooga with a bachelor's degree in electrical engineering.
In 2013, he worked briefly at a nuclear power plant near Cleveland, where he was dismissed after just 10 days for failing to "meet minimum requirements".
The only run-in Abdulazeez had with the law in the Chattanooga area appears to have been an April 20 arrest on a charge of driving while intoxicated, for which he posted a US$2,000 (S$2,730) bond.
REUTERS, NEW YORK TIMES