On July 16, 2015, Muhammad Youssef Abdulazeez opened fire on two military installations in Chattanooga, Tennessee, United States.

The Center recruited personnel for branches of the United States military, including the U.S. Army, the U.S. Air Force, and the Tennessee National Guard.

There, Abdulazeez, using his AK-47,[7] fired 30 to 45 shots[8] into the office from inside a silver rental Ford Mustang convertible,[9] wounding a U.S. Marine.

[8] Abdulazeez drove seven miles (11 km) to a U.S. Navy Reserve center on Amnicola Highway in Chattanooga,[11][12] where he rammed his vehicle through a security gate.

Abdulazeez then exited the building through the back and entered a fenced motor pool area, where he shot several Marines.

[34] According to The Washington Post, both of Abdulazeez's parents were self-described in their divorce proceedings "as natives of 'the State of Palestine'" and they "maintained a strict, conservative Muslim lifestyle.

[38][39] 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.

[32] Abdulazeez's sole known previous contact with law enforcement was an April 20, 2015 arrest for driving under the influence of alcohol (DUI).

"[35][58][62] An official participating in the investigation told The New York Times there was no evidence that Abdulazeez was in contact with any social media recruiters working for ISIL, explaining, "This case appears to be much more like the old model, where he was interested in radical Islam and sought to learn more about it online by looking at videos and readings.

[66] 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.

"[68] 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."

[65] 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.

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.

"[80] 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.

"[81] 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.

[83][84] On July 29, Carter released a two-page memorandum directing military commanders and civilian leaders to develop new security plans and measures, including "the option of additional armed personnel".

[85][86] On August 15, during a speech at a memorial for the victims, he called for a review of domestic security procedures for military installations across the country.

[67] On August 29, the Navy launched an official investigation looking into possible security changes, communications with law enforcement and emergency responders, and on-site personnel response.

[8][87][88] Though the Marine Corps ruled out arming recruiters as a security measure since most of their job is to interact with the public,[8] officials have begun developing other options.

[89] Senator Ron Johnson (R-WI) announced his intention to introduce a bill that would end the ban on firearms being carried in military installations.

Representative Goins wrote and passed legislation that would lower the carry permit age for national guard members and veterans, and active military who were 18 or older.

[92] 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.

[94] Utah Governor Gary Herbert also announced that the state would "explore additional ways to protect our men and women serving in the Armed Forces".