Last week, the United States was shaken by an appalling Chattanooga shooting rampage. The incident in the fourth largest city of Tennessee has taken the lives of five American troop members. Despite threats from notorious terrorist group ISIS, officials said there is no evidence that the carnage was inspired or directed by the Islamic militants.

On Thursday, 24-year-old Muhammad Youssef Abdulazeez killed five service members in a Chattanooga shooting spree. The authorities denied ISIS' involvement in the bloody attack, while his relatives believed that it was his own personal struggles that prompted the slayings at the military sites in Chattanooga.

As per a person close to the family, who requested the condition of anonymity to avoid unwanted publicity, the Kuwaiti-born gunman was first treated by a child psychiatrist for depression when he was 12 or 13 years old. Times Free Press also reported he struggled from drug and alcohol abuse in later years. In 2014, he was sent back to Jordan under a mutual agreement with his parents for his drugs detoxification.

The details of his personal life also fit the pattern of the gunman's behavior including a drunken driving arrest earlier this year and the loss of a job at a nuclear power plant in Ohio in May 2013 over a failed drug test. It was also noted that he had owned guns for years and called himself an "Arab or Muslim Redneck," going back to when he was a child, shooting at squirrels and targets.

Recently, the Chattanooga shooting gunman had been working the night shift at a manufacturing plant and was taking medication to help with sleeping problems in the daytime. He also had a prescription for muscle relaxants because of a back problem. It's unknown what substances were in the man's system at the time of the killings, but toxicology tests should provide an answer.

Meanwhile, authorities said Monday that the Chattanooga shooting gunman did an online research for militant Islamist "guidance" on committing violence that he thought would wipe away his sins on Earth, including drug and alcohol abuse, an arrest and a lost job. However, there is no proof so far that notorious ISIS terrorists inspired and directed Abdulazeez to launch the killings.

"I don't think that there is any evidence it was ISIL-inspired," a senior official briefed on the investigation told ABC News. "He may have been seeking some religious guidance to conduct an act. He could readily find that anywhere online. We may never know what his ultimate motivation was."

In line with the Chattanooga shooting, court records also suggest that the gunman's volatile family life has affected his mental health. According to Boston Herald, his mother filed for divorce in 2009, accusing her husband of sexually assaulting her and abusing their children but she later agreed to reconcile.

As violence and terror cloaked Chattanooga after the shooting spree, residents gathered on Saturday to honor the victims — four Marines and one U.S. Navy sailor, who were killed at two military facilities on Thursday.  

The four decorated Marines and the sailor who were killed at the Chattanooga shooting were — Staff Sgt. David Wyatt, Navy Petty Officer 2nd Class Randall Smith, Sgt. Carson Holmquist, Gunnery Sgt. Thomas Sullivan and  Lance Cpl. Squire Wells — three of whom survived combat missions.