Mohammod Youssuf Abdulazeez, a Kuwaiti-born naturalized U.S. citizen, died on Thursday in a firefight with police after a rampage at two military facilities in Chattanooga, Tennessee.
The 24-year-old engineer traveled to Jordan, possibly between April and November, U.S. government sources and friends of Abdulazeez in Chattanooga told Reuters. One childhood friend, speaking on the condition of anonymity, said he went there for a job opportunity.
Investigators will try to establish if he was part of an organization or the latest "lone wolf" militant, radicalized U.S. Muslims acting on their own who President Barack Obama has said pose a greater risk to the country than a large-scale operation.
Friends were shocked by the actions of Abdulazeez, who they said lived about 150 miles (241 km) away in Franklin, Tennessee, but had returned to his hometown to visit family for the holy fasting month of Ramadan, which ended Thursday.
"He was a friend of mine, a good Muslim. But there were no red flags, nothing unusual. It is shocking," said another childhood friend, who prayed with him at the Islamic Center of Greater Chattanooga over the past month.
A little more than 24 hours after the shooting, the FBI said it continued to investigate it as an act of terrorism and that it was "premature" to speculate on the motive.
"We are exploring all travel that he has done and we have asked our intelligence partners throughout the world to provide us with any information they may have," Ed Reinhold, FBI special agent in charge, said during a news conference.
Born to Palestinian parents and raised in a Chattanooga suburb, Abdulazeez may have family in Jordan and may have made several stops, said a government source, adding that a visit to Yemen has not been ruled out.
A trip to Yemen, long viewed as a training ground for Islamic militants, would raise special concern.
Law enforcement officials have said they are investigating whether Abdulazeez, was inspired by Islamic State or similar militant groups. Islamic State had threatened to step up violence during Ramadan.
But the FBI said Friday it had "no indication" so far that the attack was linked to that group.
'A HAPPY HOME'
Abdulazeez sprayed gunfire at a joint military recruiting center in a strip mall, riddling the glass facade with bullet holes, then drove to a Naval Reserve Center about 6 miles (10 km) away, where he killed the Marines before he himself was shot dead. Three other people were injured.