Muhammad Youssef Abdulazeez

On July 16, 2015, Muhammad Youssef Abdulazeez opened fire on two military installations in Chattanooga, Tennessee. He first committed a drive-by shooting at a recruiting center, then traveled to a U.S. Navy Reserve center and continued firing, where he was killed by police in a gunfight. Four Marines died on the spot. A Navy sailor, a Marine recruiter, and a police officer were wounded; the sailor died from his injuries two days later.

Abdulazeez's sole known previous contact with law enforcement was an April 20, 2015 arrest for driving under the influence of alcohol (DUI). A family spokesman said that the arrest triggered a severe increase in his depression.

The shooting was investigated by the FBI as a terrorism case from the outset. The Naval Criminal Investigative Service was also involved in the investigation. On July 23, 2015, in the immediate aftermath of the attack, FBI special agent Ed Reinhold stated that the attack was being treated as the work of "a homegrown violent extremist" and that the FBI is exploring the idea that Abdulazeez was self-radicalized. The following month, Secretary of Defense Ash Carter said that investigators might never be able to determine "what combination of disturbed mind, violent extremism and hateful ideology was at work." In November 2015, FBI Director James B. Comey said, "We're still trying to make sure we understand Abdulazeez, his motivations and associations, in a really good way."

On December 16, 2015, Comey said that the FBI investigation had concluded that "there is no doubt that [Abdulazeez] was inspired, motivated by foreign terrorist organization propaganda." Comey added that it was difficult to determine which specific terrorist group or groups inspired Abdulazeez. On the same day, Secretary of the Navy Ray Mabus announced that the Purple Heart would be conferred upon the victims of the shootings.

After his 2014 visit to Jordan, Abdulazeez told friends that Jordan, Qatar, and Saudi Arabia ought to have sent more help to Hamas during the 2014 Israel–Gaza conflict. They also noted a change in his behavior and that he made critical statements against the Islamic State of Iraq and the Levant (ISIL).

According to professor Charles Kurzman, the shootings were part of a "shift away from large-scale elaborate attempts to use weapons of mass destruction or other high-profile plots — the hallmark of al-Qaida and its affiliates — toward a lower tech do-it-yourself strategy" propagated by ISIL and other groups. President Barack Obama expressed similar thoughts in a December 2015 speech, saying:

On July 18, two days after the shootings, the governors of Florida, Texas, and Indiana ordered the arming of National Guardsmen at military offices and other facilities, along with the installation of bulletproof glass and more efficient video surveillance equipment. Louisiana, Oklahoma, and Arkansas followed suit the next day. Utah Governor Gary Herbert also announced that the state would "explore additional ways to protect our men and women serving in the Armed Forces". In 2014, Utah had passed legislation allowing soldiers at National Guard facilities to carry weapons.

Abdulazeez graduated from Red Bank High School. He earned an electrical engineering degree from the University of Tennessee at Chattanooga in 2012 and learned to manage electrical power systems as an intern with the Tennessee Valley Authority. On May 20, 2013, he began working as an engineer at the Perry Nuclear Generating Station in North Perry, Ohio, but was let go ten days later after failing a drug test. According to a spokesperson for FirstEnergy, which runs the station, Abdulazeez worked and received general training at an administrative office building only, and did not have access to sensitive information. In the three months prior to the shootings, Abdulazeez was employed with Superior Essex as a supervisor for its Franklin office.

In the months before the shooting, Abdulazeez regularly attended Friday prayers at a mosque. and was thought to have written a blog post in which he urged study of the Quran to give meaning to life. According to his family, Abdulazeez had searched online about martyrdom, and had been wondering whether becoming a martyr would absolve him of his sins. On July 20, several writings belonging to Abdulazeez, dating as far back as 2013, were discovered. In them, he wrote about having suicidal thoughts after losing his job due to his drug use and his desire to "becom[e] a martyr". Authorities searching his computer found that he owned CDs and had downloaded videos by al-Qaeda recruiter Anwar al-Awlaki. An FBI spokesman stated that "[t]here are some pretty radicalized thoughts" in the writings.

The National Executive Director of Council on American–Islamic Relations, Nihad Awad, said, "Such inexcusable acts of violence must be repudiated by Americans of all faiths and backgrounds." The National Vice-President of the Ahmadiyya Muslim Community USA stated, "While we do not yet know what motivated this man, we urge calm, defer to authorities to justly resolve this, and pray for the departed U.S. Marines."

According to a family representative, Abdulazeez was abusing sleeping pills, opioids, painkillers, and marijuana along with alcohol. He had also been thousands of dollars in debt and was planning to file for bankruptcy. In 2012 or 2013, Abdulazeez began therapy for his drug and alcohol abuse. He had also received treatment for depression and often stopped taking his medication. Following the shootings, Abdulazeez's parents claimed that their son had been suffering from depression. According to a source that was provided by CNN, Abdulazeez was suffering from bipolar disorder.

Abdulazeez drove seven miles (11 km) to a U.S. Navy Reserve center on Amnicola Highway in Chattanooga, where he rammed his vehicle through a security gate. He drove to one of the center's buildings, where the Inspector-Instructor staff of Mike Battery, 3rd Battalion, 14th Marines and Sailors were working.

The terrorist threat has evolved into a new phase. As we've become better at preventing complex, multifaceted attacks like 9/11, terrorists turned to less-complicated acts of violence like the mass shootings that are all too common in our society. It is this type of attack that we saw at Fort Hood in 2009, in Chattanooga earlier this year and now in San Bernardino.

Abdulazeez did not attract the attention of the FBI before the shootings. Abdulazeez traveled to Jordan five times. His first trip was in 2003 and the last trip was between April and November 2014, when Abdulazeez visited a maternal uncle. This last visit was arranged by Abdulazeez's family, who wanted him to get away from friends they believed were bad influences on him. Abdulazeez also traveled to Kuwait in 2008.

Abdulazeez migrated to the U.S. with his family in 1996 and became a U.S. citizen in 2003. During the Second Intifada, Abdulazeez, then fifteen, traveled with his father to Jamma'in, the village in the West Bank where the father was born, with the goal of acquiring a Palestinian ID.

Muhammad Youssef Abdulazeez (September 5, 1990 – July 16, 2015), a resident of Hixson, Tennessee, was identified as the gunman.

Abdulazeez, a naturalized American citizen, was born in Kuwait on September 5, 1990, to Palestinian-Jordanian parents. Abdulazeez held a temporary Jordanian passport as a travel document (commonly issued to Palestinians by the Jordanian government); Jordanian authorities emphasized that Abdulazeez was not a Jordanian citizen.