(CNN) -- Chattanooga shooter Mohammad Abdulazeez was displeased with the U.S. government, particularly its war on terror, according to writings uncovered by investigators, sources tell CNN.
The writings are not thought to be recent -- some are more than a year old, predating his much-publicized trip to Jordan -- and should not be considered a diary of any sort, according to a person familiar with the family's interviews with investigators and a law enforcement official briefed on the investigation.
The writings also include other anti-U.S. sentiments and are consistent with someone who is having suicidal thoughts, the sources said.
As the country mourns the deaths of five service members gunned down Thursday in Tennessee, investigators in both the United States and Jordan are trying to learn what prompted the attack.
Abdulazeez first shot up a military recruiting center at a Chattanooga strip mall, then drove to a local Navy operations support center and launched another attack, killing four Marines and a sailor. Abdulazeez died in a gunfight with law enforcement.
New details have emerged over the past few days. Among them:
• Abdulazeez suffered from depression and "was not the son we knew and loved," his family said in a statement over the weekend. "We extend our deepest sympathies and condolences to the families of the honorable service members and police officers who were victims of the shooting our son committed on Thursday." A police officer was among the wounded.
• The family has also told investigators that the 24-year-old had been abusing drugs for some time, according to a source familiar with the family's interviews with investigators. The drugs reportedly included "party drugs" and marijuana.
• Abdulazeez's family sent him to Jordan last year to get him away from Chattanooga friends who they said were bad influences on him, the relatives told investigators.
• Some relatives and friends told investigators they detected changes in his behavior after he returned from Jordan last year, a law enforcement official said.
• Jordanian security investigators have interviewed Abdulazeez's extended family, asking where he went and whom he spoke with, government sources there told CNN.
• Authorities are investigating a text message from Abdulazeez to a friend before the attack, law enforcement sources said. The message included an Islamic verse that says, "Whoever shows enmity to a friend of mine, then I have declared war against him."
• Abdulazeez had a hard time keeping a job because of his manic depressive/bipolar disorder and drug use for which he had sought treatment with a psychiatrist, according to the source familiar with the family's interviews.
• "It grieves us beyond belief to know that his pain found its expression in this heinous act of violence," the Abdulazeez family said in its statement.
"I think mental health professionals would be not happy with what the parents are assessing, in saying, 'Well, he was depressed, and therefore that's why he became a killer like this,' " CNN law enforcement analyst Tom Fuentes said. "People with depression do not turn, necessarily, into psychopathic killers -- as he did."
U.S. Attorney Bill Killian said the shootings are being investigated as terrorism.
So far, there is nothing connecting the attacker to ISIS or other international terror groups, said Ed Reinhold, special agent in charge of the regional FBI office. Abdulazeez was not on any U.S. databases of suspected terrorists.
Some governors are increasing security measures for National Guard recruiters and military facilities. Several have called for arming National Guard members.
Florida Gov. Rick Scott ordered National Guard members at six state recruitment centers to be relocated to armories until security is improved. In addition, qualified Guard members will be armed.
Texas Gov. Greg Abbott has called for armed National Guard personnel at military facilities throughout the state.
And Oklahoma Gov. Mary Fallin authorized the arming of certain full-time personnel in military installations throughout the state.
"It is painful enough when we lose members of our armed forces when they are sent in harm's way," she said in a statement. "But it is unfathomable that they should be vulnerable for attack in our own communities."
Grief across the country
The victims came from across the country but united in Chattanooga, brought together by their service in the military.
Marines Gunnery Sgt. Thomas Sullivan of Massachusetts was a two-time Purple Heart recipient. He served three tours of duty.
Lance Cpl. Squire K. Wells, better known as "Skip," graduated from high school three years ago. The Georgia native joined the Marines in 2014 and had already earned a National Defense Service
Marines Staff Sgt. David Wyatt of Arkansas served two tours of duty in Iraq and one in Afghanistan. His wife posted about his death on Facebook. "He was such a great husband and father," one commenter wrote.
Marines Sgt. Carson Holmquist was also a husband and father and served two tours of duty in Afghanistan. Upon one of his homecomings, his family held up a sign that read, "We've waited 244 days for this moment. Welcome home Sgt. Holmquist."
Navy Petty Officer Randall Smith of Ohio was a logistics specialist. He saw the gunman in last week's attack and warned people around him, family members said, but was unable to get away.
On Sunday, Smith's mother visited a makeshift memorial for the victims. Paula Proxmire cried as she left a baseball glove, a baseball and an American flag in honor of her son.
Red, white and blue balloons covered the memorial, along with a poster with pictures of the victims.
CNN's Catherine E. Shoichet, Boris Sanchez, Aaron Cooper, Greg Botelho, AnneClaire Stapleton, Jomana Karadsheh, Ashley Fantz, Melissa Gray, Devon Sayers and Eliott C. McLaughlin contributed to this report.