Mass shootings and murders have tested America's relationship with guns.
America's struggle over gun violence and the right to bear arms has been raging for decades. Here's a look at key events in the United States' long, tortured relationship with crime and guns:
1791: The Second Amendment to the U.S. Constitution was adopted. It read, “A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.”
1911: New York State passed the Sullivan Act, one of the first pieces of gun control. It required a permit to carry a concealed weapon, and remains law.
1934: The National Firearms Act, passed in response to a string of crimes using automatic weapons, levied a tax on the manufacture and sale of firearms, including machine guns, shotguns and certain rifles. It is still in effect.
1938: The Federal Firearms Act was passed, requiring gun dealers to obtain a license and maintain records on all their sales. It also made it illegal to sell a gun to a convicted criminal.
1963: President John F. Kennedy was assassinated. Crime rates began a steep climb.
1965: Sen. Robert F. Kennedy and Dr. Martin Luther King Jr. were assassinated.
1968: President Lyndon Johnson signed the Gun Control Act, which placed more stringent regulations on gun sales, including a ban on selling rifles and shotguns by mail.
1972: The Bureau of Alcohol, Tobacco & Firearms was created.
1975: The violent crime rate peaked. The National Rifle Association creates a lobbying group. That same year, it successfully fought an effort by Sen. Edward Kennedy to have ammunition regulated as a “hazardous substance.”
1980: Violence rates peaked again.
1981: President Ronald Reagan was shot and his press aide James Brady seriously wounded.
1984: A gunman armed with an Uzi submachine gun killed 21 people and wounded 19 at a McDonald’s in San Ysdiro, Calif. The crack era began.
1986: The Firearms Owners Protection Act passed, easing restrictions on in-person purchases of guns by people from out of state and limiting inspections of licensed dealers by the ATF.
1989: A gunman wielding an AK-47 rifle killed five children and injured 29 others on a schoolyard in Stockton, Calif.
1993: President Bill Clinton signed the Brady Bill, which imposed a five-day waiting period on the purchase of a gun and required local law enforcement to conduct background checks on all potential buyers.
1994: Clinton signed the Violent Crime Control and Law Enforcement Act, including the Assault Weapons Ban, which prohibited, for 10 years, the manufacture and sale of semiautomatic weapons with magazines capable of holding 10 or more rounds.
Congress banned the Centers for Disease Control from promoting gun control and effectively stopped it from funding research on gun violence.
1997: The Supreme Court found the Brady Bill’s local background checks unconstitutional.
1999: Two students at Columbine High School in Littleton, Colo., went on a rampage at their school, killing 12 classmates and one teacher.
2001/2002: John Allen Muhammed and Lee Boyd Malvo murdered 15 people in a series of sniper shootings in the Washington D.C. area.
2004: The Assault Weapons Ban expired and Congress chose not to renew it.
2005: Congress granted immunity to the firearms industry from civil suits in cases where a gun was used in a crime.
2007: Seung-Hui Cho, a Virginia Tech student with a history of mental problems, killed 32 people in two attacks on the school’s Blacksburg campus.
2007: In response to the Virginia Tech shooting, Congress passed the NCIS Improvement Amendments Act, authorizing $1.3 billion to improve states’ systems to find and track people trying to buy guns – a so-called “gun-buyer database.” It did not apply to sales at gun shows by unlicensed vendors.
2008: The Supreme Court invalidated Washington D.C.’s 32-year-old ban on handguns. The city responded with new laws that revived the ban while abiding to the strictures of the court’s ruling.
2009: Maj. Nidal M. Hasan allegedly went on a rampage at Fort Hood, Texas, killing 12 soldiers and one civilian.
2009: Michael McLendon killed 10 people and himself in a shooting spree that spanned two southern Alabama towns.
2011: Rep. Gabrielle Giffords was among several people shot at an event in Tuscon, Ariz. Six others were killed, including a judge and a young girl.
2011: New York City Mayor Michael Bloomberg sent undercover investigators to an Arizona gun show to show how easy it was to buy handguns from unlicensed vendors without background checks. Bills by several Democratic members of Congress attempt to ban high-capacity handguns, close the so-called gun-show loophole and prevent gun sales to people on terrorist watch lists. All the proposals were defeated.
2012: Florida teenager Trayvon Martin is shot and killed by a neighborhood watch volunteer, who invoked the state’s 2005 “Stand Your Ground” law as a defense.
2012: James Holmes allegedly opened fire on a crowded movie theater in Aurora, Colo., killing 12 people and wounding 58.
2012: White supremacist Wade Michael Page killed six people in a Sikh temple in Oak Creek, Wisc.
2012: Adam Lanza killed 20 children and six adults at Sandy Hook Elementary School in Newtown, Conn., before taking his own life. He was also believed to have killed his mother.
Sources: Facts on File News Services, Philip Cook, Washington Post, CNN