Following are some of the worst such incidents in the United States in 2012:
April 2 - A gunman kills seven people and wounds three in a shooting rampage at a Christian college in Oakland.
July 20 - A masked gunman kills 12 people and wounds 58 when he opens fire on moviegoers at a showing of the Batman film "The Dark Knight Rises" in Aurora, a suburb of Denver, Colorado.
August 5 - A gunman kills six people during Sunday services at a Sikh temple in Oak Creek, Wisconsin, before he is shot dead by a police officer.
August 24 - Two people are killed and eight wounded in a shooting outside the landmark Empire State Building in New York City at the height of the tourist season.
September 27 - A disgruntled former employee kills five people and takes his own life in a shooting rampage at a Minneapolis sign company from which he had been fired.
October 21 - Three people are killed in a Milwaukee area spa including the estranged wife of the suspected gunman, who then killed himself.
December 14 - A shooter opens fire at the Sandy Hook Elementary School in Newtown, Connecticut, killing several people including children.