explain how the security of United States, could help prevent tragedies that involve the United States military

We the people, of the United States of America think that we Americans should make the security more protected. That we should form a more protected security for the civilians of the United States. Also to do background checks on people who work for the military, or are in the military so we can prevent tragedies like the one this last Monday at the Washington Navy Yard. Are National Security is the best in the World, but we Americans don't want to deal with the heartbreak of tragedies like this. Mr.President Barack Obama please take this into consideration! Thank You!