A police officer runs near the scene of the shooting rampage at the Washington Navy Yard on Monday, September 16. Authorities said at least 12 people -- and the suspect -- were killed in the shooting. 
A U.S. Park Police officer stands guard near the scene of the shooting. 
Military security observes the scene from a nearby rooftop. 
The White House flies the U.S. flag at half-staff following the shooting. 
A police boat patrols the waters at the Washington Navy Yard. 
Late Monday afternoon the FBI identified Aaron Alexis, a 34-year-old military contractor from Texas, as the dead suspect involved in the shooting. 
Workers who had been sheltered during a lockdown exit the Navy Yard. 
People step off buses at Parking Lot B of Nationals Park, which was set up as a gathering point for family members of Navy Yard employees in the wake of the shooting. 
A man and woman embrace at the gathering point inside Nationals Park. 
A man walks with a woman after they were reunited at Nationals Park. 
A woman reunites with her child inside Nationals Park. 
Washington Mayor Vincent Gray and Washington Police Chief Cathy Lanier speak to the media near the Washington Navy Yard. 
Police officers walk on a rooftop at the Washington Navy Yard. 
A member of the military stands guard at the scene of the shooting. 
A woman watches from an office building as police respond to the shooting. 
Police officers leave the scene after responding to the shooting. 
A police officer and police canine inspect vehicles in a parking lot outside the Washington Navy Yard. 
A Homeland Security officer tells a woman where to park and wait for her husband, who works in the Washington Navy Yard. 
A police helicopter hovers above snipers on the roof of a building at the Washington Navy Yard. 
Police stand guard on M Street in Washington. 
Police boats patrol the Anacostia River off the Washington Navy Yard complex. 
A U.S. Capitol Police officer keeps watch on the East Plaza of the Capitol in Washington. 
Troops stand guard in front of a parking garage near the Washington Navy Yard. 
Police vehicles move toward the Navy Yard. 
Armed agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives work on the 11th Street Bridge adjacent to the Washington Navy Yard. 
Emergency vehicles fill the streets around the Washington Navy Yard. 
A helicopter lifts a person off a roof at the Navy Yard. 
A police officer carries an automatic rifle at the Washington Navy Yard. 
Police officers adjust their gear. 
Police block off a road leading to the Washington Navy Yard. 
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- Washington Navy Yard shooter Aaron Alexis had background of violent incidents, misconduct
- Daniel Webster: How could someone like Alexis legally buy and carry loaded firearms?
- He says to appease gun lobby, policies have low standards for possession of guns
- Webster: Stronger standards for legal gun ownership could help reduce horrific shootings
Editor's note: Daniel W. Webster is professor and director of the Center for Gun Policy and Research at Johns Hopkins Bloomberg School of Public Health.
(CNN) -- We are still learning key details about Aaron Alexis, the man named as the shooter in this week's horrific mass killing at the Washington Navy Yard.
So far there is a record of at least two prior incidents in which Alexis fired a gun under circumstances that should have brought criminal charges. His time as a Navy reservist was checkered with accounts of insubordination and disorderly conduct. He was reportedly seeking treatment for mental illness (he was hearing voices and having problems sleeping). More importantly from the perspective of risk for violence, a former roommate reported that Alexis was a heavy drinker.
While much of the focus has been on how a person with this background obtained clearance to work at a military facility, a similar question could be asked about how he could legally buy a firearm in Virginia and allegedly obtain a permit to carry loaded firearms in Texas.
Opinion: Gun control is not the answer
The gun lobby and other opponents to stronger gun laws like to talk about the rights of "law-abiding gun owners," but the policies in place in most states allow individuals with backgrounds far worse than that of Alexis to own legally as many firearms as they can afford and carry loaded firearms most anywhere.
To appease the gun lobby, lawmakers have created an environment where individuals with numerous convictions for misdemeanor crimes involving violence, firearm misuse, illegal drugs and alcohol abuse, and who have previously been subject to restraining orders for domestic violence, can legally arm themselves to the teeth.
Several states have stricter standards for legal possession of handguns than federal law, and states such as New York, New Jersey and Massachusetts give law enforcement some discretion in determining who should legally be able to buy and carry handguns.
My colleagues and I published a study last year where we found that in states with the weakest standards (similar to federal standards), nearly one-third of state prison inmates incarcerated for crimes committed with guns would have been prohibited from possessing firearms when committing their most recent offense if their states had standards for legal gun possession similar to those in place in high-standards states. With reasonable regulations such as background checks for all gun sales and proper regulation of gun dealers, many of these inmates would not have had guns to use in crime.
Opinion: What could have prevented Navy Yard carnage?
Cutter: Gun increase breaks all logic 
Remembering the victims In order to reduce significantly the gun violence that occurs every day in communities across the United States, we must focus on the issues that matter the most where there is broad consensus. Public opinion surveys show large majorities of gun owners support stronger standards for legal gun ownership and policies designed to keep guns from prohibited persons, including universal background checks and stronger regulation and oversight of gun dealers.
We can't say for sure whether such policies would have prevented the recent mass shootings that have gripped our nation, but they would reduce a significant number of shootings that don't receive national news attention, though they are no less devastating to the individuals, families and communities.
Unfortunately, the gun debate in the United States has been just that -- a debate. Instead of engaging in the all too familiar, polarizing discussions that have characterized gun policy, let's act upon the things we all agree upon -- keeping guns from people who shouldn't have them.
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The opinions expressed in this commentary are solely those of Daniel W. Webster.
