RIYADH, Saudi Arabia (AP) — A Saudi-American dual national who was recently fired from a U.S. defense contractor shot two American ex-colleagues in Saudi Arabia's capital, killing one and wounding the other in what appeared to be a settling of scores, security and diplomatic officials said.

The gunman, Abdulaziz Fahad Abdulaziz Alrashid, was taken into police custody after being injured a shootout with Saudi security forces, said a statement released in Washington on behalf of the Saudi Embassy. Alrashid, 24, was recently dismissed from his job for drug-related issues, the statement said, citing the Saudi Interior Ministry for that information.

A person with knowledge of the shooting, who was not authorized to discuss the incident publicly, told The Associated Press that the shooter believed that the victim he shot dead had turned him in for the alleged drug use.

The victims were employees of Vinnell Arabia, a U.S. defense contractor supporting Saudi National Guard military programs in the Saudi capital, Riyadh, and were shot about a kilometer (half-mile) from its facility in the city, said State Department spokeswoman Jen Psaki. The site, on the eastern side of the capital, is also near the Saudi National Guard headquarters.

"We are in close contact with the Saudi government as we continue to gather details about the shooting and motive," Psaki said. "We are in the process of evaluating our security posture and will take appropriate steps to ensure the safety of all U.S. Mission personnel."

Vinnell Arabia declined to comment when contacted by the AP. A spokesman for parent company Northrop Grumman could not be immediately reached. Vinnell Arabia's Web site features a recruitment video with personal accounts from former U.S. military personnel who now work for the company — including veterans of wars in Iraq and Afghanistan.

The attack was likely to send chills through the Western expatriate workforce in the kingdom, which has been on alert for possible terrorism. In September, Saudi police said they had arrested 88 people suspected of being part of an al-Qaida cell that was planning attacks inside and outside the kingdom.

Saudi Arabia and four other Arab countries are taking part in U.S.-led airstrikes against the Islamic State group and al-Qaida fighters in Iraq and Syria. Militants have vowed revenge.

Attacks by al-Qaida militants from 2003 to 2007 were aimed at destabilizing and toppling the Western-allied monarchy. Among the most stunning attacks were deadly bombings of residential compounds in Riyadh where foreigners lived in 2003.

Saudi officials responded at the time with a massive crackdown that saw many al-Qaida operatives killed or arrested. Others fled to neighboring Yemen, giving birth to one of the group's most active branches.

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Associated Press writers Matthew Lee and Lara Jakes contributed to this report from Washington, and Aya Batrawy contributed from Dubai, United Arab Emirates.