The U.S. Army, Navy and Marine Corps could do a better job monitoring access to their installations as a way of preventing mass shootings like the one that devastated Fort Hood, Texas, according to a new Government Accountability Office report. All branches of the U.S. military rely on physical access control systems (PACS) to screen people who want to enter installations, checking their identities with FBI and other government databases. But the GAO found that the Pentagon "didn't know the extent to which its installations were using these systems because the Army, Navy and Marine Corps have not monitored their use," the report states. Read more on Military.com.