July 27, 2012 -- intro:As the initial horror of last week's movie theater massacre in Aurora, Colo., begins to subside, the calls for action to prevent another mass shooting are growing.
But in the week following the worst mass shooting in U.S. history that left 12 dead and 58 injured, the political push for gun control is far weaker than after similar tragedies of the past.
Nearly every major reform to U.S. gun laws has come on the heels of a mass shooting. From Columbine to John F. Kennedy, America's most terrifying shootings have been the catalysts for the country's most sweeping reforms.
quicklist: 1 title: St. Valentine's Day Massacre category: Inspired a hefty tax on automatic weapons text:During prohibition in 1929 mobsters like Al Capone ruled the streets of Chicago, stockpiling fortunes from bootlegged alcohol sales and taking no prisoners. To solidify his position as Chicago's No.1 gangster, Capone's cronies executed seven rival mobsters in what came to be known as the St. Valentine's Day Massacre.
Capone's men were loaded down with two Thompson submachine guns when they burst into rival mobster George "Bugs" Moran garage, lined seven men up against a wall and opened fire, shredding their victims with 90 bullets.
The massacre inspired Congress to take action against the machine guns and short-barreled shotguns that were common in gang violence. In 1934 President Franklin Roosevelt signed the National Firearms Act which imposed a hefty $200 fined on such gangster weapons.
quicklist: 2 title: President Kennedy's Assassination category: Inspired Congress to outlaw mail order sales of rifles and shotguns text: After Lee Harvey Oswald assassinated President John F. Kennedy using a sniper rifle he bought through the mail, Sen. Thomas Dodd, D-Conn., introduced a ban on mail order sales of rifles and shotguns, re-igniting the gun control debate.
While Kennedy's assassination in 1963 restarted the national discussion about gun control, it was not until the back-to-back assassinations of Martin Luther King, Jr. and Robert Kennedy pushed Congress to actually pass legislation.
Four months after Robert Kennedy was killed, President Lyndon B. Johnson signed the Gun Control Act of 1968 into law, banning mail order sales of rifles and shotguns and prohibiting most felons, drug users and people found mentally incompetent from buying guns.
quicklist: 3 title: President Reagan's Assassination Attempt category: Inspired criminal background check requirements text: President Ronald Reagan had been in office a mere 69 days when John Hinckley Jr. attempted to assassinate him while leaving the Washington Hilton Hotel in D.C. Reagan was shot in the lung and made a full recovery.
Reagan's press secretary James Brady was not so lucky. He took a bullet to the head that left him permanently paralyzed. Following the attack, Brady became an advocate for handgun control, founding the Brady Campaign to Prevent Gun Violence that is still active today.
In 1993 President Bill Clinton signed a law that requires prospective gun owners to pass a federal background check before buying a gun. The act was named after James Brady.
quicklist: 4 title: 101 California Street Shooting category: Inspired the 1994 assault weapons ban text: On July 1, 1993 a 55-year-old man strolled into the Pettit & Martin law offices on 101 California St. in San Francisco with three handguns and opened fire, killing eight and wounding six before killing himself.
The shooter, Gian Luigi Ferri, used two TEC-9 handguns equipped with Hellfire triggers, which allow the gunman to shoot faster and make the semi-automatic weapon nearly automatic.
It was the worst mass killing in San Francisco's history and inspired some of the most sweeping gun control laws at both the state and federal level. Thirteen months after the attack, Congress passed an assault weapons ban, outlawing the three handguns Ferri used along with 17 other types of military-style guns such as the AK-47 and the Uzi submachine gun.
The 1994 assault weapons ban expired in 2004 and all five attempts to renew it have failed.
The shooting inspired California to pass the most stringent state gun control law in the country. The law, which took effect six years after the California Street shooting, banned semi-automatic rifles and pistols that have various accessories like pistol grips or folding stocks. It also outlawed magazines that hold more than 10 rounds of ammunition.
quicklist: 5 title: Columbine High School Shooting category: Re-ignited gun control debate, but no changes to law text: When teenagers Eric Harris and Dylan Klebold opened fire on their fellow students at Columbine High School on April 20, 1999 they struck fear into the hearts of parents and schoolchildren nationwide. By the time the pair committed suicide, 12 of their classmates and one teacher lay dead.
It was, at the time, the most deadly school shooting in American history, creating a cloud of fear that hung over schools around the country. But the massacre did not result in changes to America's gun control policies.
A month after the shooting, the Senate narrowly passed a bill requiring background checks for firearm sales at gun shows, with Vice President Al Gore casting the deciding vote. The bill, which also required child safety trigger locks to be sold with guns, never passed the House.
quicklist: 6 title: Virginia Tech Shooting category: Inspired more stringent background check system text: Virginia Tech senior Seung Hui Cho was deemed "mentally ill" and "an imminent danger to self or others" more than a year before he murdered 32 of his fellow Virginia Tech University students in the deadliest school shooting in U.S. history.
Cho legally purchased two handguns in the months following the psychological evaluation.
In the year following the 2007 Virginia Tech massacre, Congress passed and President George W. Bush signed the first major change to U.S. gun laws in more than a decade. The law expanded the federal background check database to include an estimated 2 million more people, particularly felons and the mentally ill.