Four Marines were killed in a shooting spree that spanned two military centers at a Naval facility in Chattanooga, Tenn., Thursday morning. A sailor injured in the attack died early Saturday morning, according to the Navy. Here are five things to know about the attack:

  1. VICTIMS: Four Marines were killed Thursday and a sailor died Saturday from his injuries. The victims are: Gunnery Sgt. Thomas J. Sullivan of Hampden, Massachusetts; Staff Sgt. David A. Wyatt of Burke, North Carolina; Sgt. Carson A. Holmquist of Polk, Wisconsin; Lance Cpl. Squire K. "Skip" Wells of Cobb County, Georgia and Petty Officer Randall Smith from Paulding County, Ohio. Two people were injured: A Marine was shot in the leg; and a police officer was shot in the ankle.
  2. GUNMAN: The gunman, identified as 24-year-old Mohammad Youssef Abdulazeez, was also killed. Abdulazeez had an engineering degree from the University of Tennessee-Chattanooga. He was believed to have been born in Kuwait and may have had dual Kuwaiti-American citizenship. He was Muslim but was not known by acquaintences to be radicalized.
  3. TERRORISM: FBI Special Agent in Charge Ed Reinhold said investigators would determine whether the shootings were an act of terrorism — "whether it was domestic, international" - or simply a criminal act.  Abdulazeez was not on law enforcement's radar and there was no intelligence indicating an attack was forthcoming. The investigation is being treated as terrorism until it is proven otherwise, according to federal law enforcement officials.
  4. LAST DAY OF RAMADAN: The killings happened on the last day of the Muslim holy month of Ramadan. Islamic State supporters called for "lone wolf" attacks against perceived enemies during this year's Ramadan at the beginning of the holy month.
  5. FALSE REPORT: A false report was spread that an "ISIS-linked" Twitter account tweeted about the attack before it happened. The tweet in question was actually posted after the attack and the account has since been suspended.