1. The shootings at a Connecticut elementary school have reopened a long-dormant debate over gun control. Some advocates of stronger laws say the massacre represents a turning point, while opponents are mostly keeping quiet for now. 
  2. History shows that mass shootings and assassinations have played a key role in the passage of stronger gun-control laws. But not every shooting leads to new laws. Typically, it has taken more than one high-profile event and several years of debate for a gun-control proposal to become a law. 
  3. Below, a look at some past shootings that led to new laws, and some that didn't.
  4. 1929: St. Valentine's Day Massacre

  5. Police and people gather in front of the S.M.C. Cartage Co. garage on North Clark in Chicago on Feb. 14, 1929, following the St. Valentine's Day massacre. (AP Photo/Chicago History Museum) 
  6. During the Prohibition era, illegal sales of alcohol led to a rise in criminal gangs who used submachine guns. In 1929, members of Al Capone’s gang in Chicago used Tommy guns to kill seven members of a rival gang. The so-called St. Valentine’s Day Massacre prompted several gun control proposals, but no new laws were passed in the immediate aftermath of the shootings.
  7. 1933: Roosevelt assassination attempt

  8. In 1933, an unemployed bricklayer named Giuseppe Zangara shot and killed Chicago Mayor Anton Cermak in what is believed to have been an attempt to assassinate President-elect Franklin D. Roosevelt. The shooting helped build support for one of the bills first proposed after the St. Valentine's Day Massacre. The National Firearms Act of 1934 set up the first federal registration system for gun dealers and imposed heavy taxes on certain types of guns.
  9. 1963: Assassination of John F. Kennedy

  10. President John F. Kennedy speaks at dedication ceremonies of the Aerospace Medical Center at Brooks Air Force Base, San Antonio, Tex., Nov. 21, 1963. (AP Photo)
  11. The assassination of President John F. Kennedy in 1963 sparked debate over gun laws. Assassin Lee Harvey Oswald had bought a rifle through the mail and had it delivered to a post office box under a false name. Debate began over mail-order gun sales, but no new laws were passed immediately after the assassination. 
  12. 1966: Texas tower sniper

  13. Smoke rises from a sniper's gun as he fires from the tower of the University of Texas administration building in Austin at people below in 1966. (AP Photo/File)
  14. In 1966, former Marine Charles Whitman killed his wife and mother, then killed 13 people and wounded 32 others in a shooting rampage from the tower at the University of Texas in Austin. As with the Kennedy assassination, the shootings led to renewed debate over gun control, but no immediate changes in the law.
  15. 1968: Assassinations of Robert Kennedy and Martin Luther King

  16. This view shows the window in Memphis, Tenn., from which a man shot Martin Luther King Jr. on April 4, 1968. (AP Photo)
  17. The 1968 assassinations of Sen. Robert Kennedy and civil rights leader Martin Luther King Jr. came while Congress was debating a gun control measure that was part of President Lyndon Johnson's "Great Society" legislation, helping spur passage of the Gun Control Act of 1968, which expanded the categories of people who could not buy guns, barred mail-order sales of rifles and shotguns and banned imported handguns.
  18. 1981: Reagan assassination attempt

  19. Hoping to impress actress Jodie Foster, a mentally ill man named John Hinckley Jr. attempted to assassinate President Ronald Reagan. One of his shots left White House Press Secretary James Brady paralyzed. Brady and his wife, Sarah, later formed a gun control group now known as the Brady Campaign to Prevent Gun Violence. But it took until 1993 for supporters to pass the Brady Bill, creating the first national system of background checks for gun buyers