The latest Fort Hood shooting is throwing a spotlight on the US military's so-far frustrated efforts to secure its bases from potential attackers, who increasingly appear to see the facilities as attractive targets.
It was the third rampage at a US base in just more than six months, following attacks at the Washington Navy Yard in September and at Naval Station Norfolk in Virginia late last month.
The discussion comes amid a larger debate about how to prevent mass shootings among the civilian population, an issue at the top of the national agenda after the December 2012 killing of 20 children and six adults at a Newtown, Connecticut, school.
US Defense Secretary Chuck Hagel said the latest incident showed that there were problems that still needed to be addressed.
Something is not working, Hagel said, "when we have these kinds of tragedies on our bases".
Fort Hood had already overhauled its security to better deal with "insider threats" after a 2009 rampage by an army psychiatrist who shot dead 13 people and wounded 32 others. He now faces the death penalty.
Base commander Lieutenant General Mark Milley suggested that the security overhaul helped limit the damage from Wednesday's shooter, who served four months in Iraq in 2011.
"I think the response from the law enforcement and the medical folks displayed clear lessons learned from the previous case," Milley said, describing a swift reaction by military police to confront the shooter and by medical responders to reach victims.
Just more than two weeks ago, Hagel unveiled a sweeping review of the Navy Yard shooting, which concluded the rampage could have been averted if concerns about the gunman's mental health been properly handled.
Hagel backed establishing an insider threat management and analysis centre within the Pentagon and moving to a system with better monitoring of personnel with security clearances.
In the Norfolk case, a civilian went on base and shot dead a sailor aboard a docked Navy destroyer before being killed.
While some observers question whether shooters can be stopped, Hagel rejected the idea that nothing more could be done.
"It isn't a matter of a question or challenge [that's] too tough. We will do it," he said.