Four people, including the gunman, were killed and eight others were injured in a shooting at Naval Air Station Pensacola. CBS News has learned the gunman was Mohammed Saeed Alshamrani, a Saudi Arabian national, and a pilot-in-training for the Saudi Air Force. He had been training in the United States since 2017. The FBI is investigating the suspect’s social media posts and whether he acted alone. But investigators have not said what his possible motive might have been. David Begnaud reports. Watch "CBS This Morning" HERE: http://bit.ly/1T88yAR Download the CBS News app on iOS HERE: https://apple.co/1tRNnUy Download the CBS News app on Android HERE: https://bit.ly/1IcphuX Like "CBS This Morning" on Facebook HERE: http://on.fb.me/1LhtdvI Follow "CBS This Morning" on Twitter HERE: http://bit.ly/1Xj5W3p Follow "CBS This Morning" on Instagram HERE: http://bit.ly/1Q7NGnY Get new episodes of shows you love across devices the next day, stream local news live, and watch full seasons of CBS fan favorites anytime, anywhere with CBS All Access. Try it free! http://bit.ly/1OQA29B Each weekday morning, "CBS This Morning" co-hosts Gayle King, Anthony Mason and Tony Dokoupil deliver two hours of original reporting, breaking news and top-level newsmaker interviews in an engaging and informative format that challenges the norm in network morning news programs. The broadcast has earned a prestigious Peabody Award, a Polk Award, four News & Documentary Emmys, three Daytime Emmys and the 2017 Edward R. Murrow Award for Best Newscast. The broadcast was also honored with an Alfred I. duPont-Columbia Award as part of CBS News division-wide coverage of the shootings at Sandy Hook Elementary School in Newtown, Connecticut. Check local listings for "CBS This Morning" broadcast times.