An uncle of the gunman who killed five servicemen last week in Chattanooga, Tennessee, has been detained for questioning in Jordan, his lawyer said Tuesday, as investigators continued to try to find a motive for the shootings.

The uncle was questioned by U.S. and Jordanian investigators, the lawyer, Abed Al-Kader Ahmad Al-Khateab, said. He is related to the gunman, Mohammod Abdulazeez, through Abdulazeez’s mother.

Abdulazeez’s parents are from Jordan, and he spent seven months in this country last year, staying with relatives. Investigators are trying to determine whether he was radicalized by contact with Islamist extremists during his stay and whether he traveled to any other countries. He was killed in a shootout with police during the attack.

Even before he went to Jordan, Abdulazeez wrote notes, which are being examined by the FBI, expressing anger at the United States and thoughts of martyrdom and suicide. In his final hours, he sent a friend a text message with a link to an Islamic verse saying, “Whosoever shows enmity to a friend of Mine, then I have declared war against him.”

His writings do not refer to any specific violent acts he planned to carry out, but they do point to a depressed and jumbled mind. His blog consists of long, elliptical essays on Islam and contains the warning, “This life is short and bitter.” A family representative said some of his written notes amounted to “gibberish.”

On Thursday, Abdulazeez, 24, drove to a military recruitment center in Chattanooga and opened fire with an assault rifle on the storefront office. Then he drove to a Navy Reserve center a few miles away and resumed shooting, taking aim at the military personnel there and the police officers who were trying to stop him.

By the time the gunfire stopped, four Marines and the gunman lay dead, a sailor was fatally injured and two other people were wounded.

Officials say Abdulazeez had three firearms with him. Investigators are trying to determine whether anyone helped him acquire the guns or plan the assault.