Dec. 14, 2012: A gunman opened fire inside a Newtown, Conn., elementary school Friday in a shooting that left 27 people dead, including 18 children.

Dec. 11, 2012: A masked man with a gun fired at the food court of a mall outside Portland, Ore., killing two. The gunman died of a self-inflicted gunshot. One other person was critically injured.

Aug. 13, 2012: A 30-minute shootout near the Texas A&M University campus in College Station, Texas, resulted in the deaths of a police constable, a bystander, the shooter, and the injury of four others.

Aug. 5, 2012:  A gunman opens fire at a Sikh temple in Oak Creek, Wis. killing six people and wounding three. Police shot and killed the suspect, Wade Michael Page, after the attack.

July 17, 2012: A gunman stood outside of a crowded downtown bar and opened fire from two different sending patrons running or crawling for cover. At least 17 people were hurt. Nathan Van Wilkins, 44, surrendered about 10 hours after the shooting near the University of Alabama campus in Tuscaloosa, police said.

July 20, 2012: During a midnight screening of the film "The Dark Knight Rises" in Aurora, Colo., a gunman opens fire on the crowded theater. At least 12 people are killed and 58 others are wounded. The suspect, James Holmes, set off a smoke device in the front of the theater before opening fire. Directly after the incident, Holmes, age 24, was arrested in a parking lot behind the theater.

June 9, 2012: A gunman opens fire at an apartment complex near the campus of Auburn University. Three people were killed  - among them Auburn football player Edward Christian, a former star at Lowndes High School in Valdosta, Ga., and former teammate Ladarious Phillips - and three others were wounded.

April 2, 2012:  One Goh, a 43-year-old former student at Oikos University, a Christian school, opened fire on the Oakland, Calif., campus, killing seven people and wounding several others.

March 6, 2012: Shane Schumerth, a 28-year-old teacher at Episcopal High School in Jacksonville, Fla., returned to the campus after being fired and shot and killed the headmistress, Dale Regan, with an assault rifle.

Feb. 27, 2012:  At Chardon High School in Ohio, a former classmate opened fire, killing three students and injuring six. Arrested shortly after the incident, the shooter said that he randomly picked students.

Dec. 8, 2011: A Virginia Tech police officer was shot and killed by a 22-year old student of Radford University. The shooting took place in a parking lot on Virginia Tech's campus in Blacksburg, Va.

Oct. 12, 2011: Scott Dekraai, 41, ap­par­ently en­raged over a cus­tody dis­pute, al­legedly walks in­to a crowded Seal Beach, Calif., hair salon where his former wife works and opens fire. Eight people are killed, one more is crit­ic­ally wounded. Dekraai has pleaded not guilty in the case.

May 10, 2011:  Three people were killed in a parking garage at San Jose State University. Two former students were found dead on the fifth floor of a garage at the  San Jose, Calif., campus. A third, the suspected shooter, died later at the hospital.

Jan. 5, 2011: Two people opened fire during a Worthing High School powder-puff football game in Houston, Texas. One former student died. Five other people were injured.

Jan. 8, 2011: Arizona Rep. Gabrielle Giffords was shot in an assassination attempt. At least 17 others are shot by a gunman, identified as Jared Lee Loughner, who opened fire on the congresswoman's constituent meeting outside a grocery store in Tuscon, Ariz. Six people are fatally wounded, including U.S. District Court Judge John Roll, and a young girl.

Jan. 5, 2011:  Two people were killed and two more injured in a shooting at Millard South High School in Omaha, Neb. Shortly after being suspended from school, the shooter returned and shot the assistant principal, principal, and the school nurse. The shooter then left campus and took his own life.

Feb. 12, 2010: During a meeting on campus, Amy Bishop, a biology professor, began shot her colleagues, killing three and wounding three others in Huntsville, Ala.

March 9, 2010: A man opens fire at Ohio State University in Columbus, Ohio, killing two employees and wounding one other.

Nov. 5, 2009: Thirteen are killed and 32 injured in a shooting ram­page at Ft. Hood, Texas, where he is based. Maj. Nid­al Ma­lik Has­an, an Army psy­chi­at­rist, is accused of the shooting. April 3, 2009: Jiverly Voong, 41, shoots and kills 13 people and ser­i­ously wounds four oth­ers be­fore ap­par­ently com­mit­ting sui­cide at an im­mig­ra­tion ser­vices cen­ter, in Bing­hamton, N.Y.

Feb. 14, 2008: Gunman killed five students and then himself, and wounded 17 more when he opened fire on a classroom at Northern Illinois University in DeKalb, Ill. The gunman, Stephen P. Kazmierczak, was identified as a former graduate student at the university in 2007.

Feb. 8, 2008: A nursing student shot and killed two women and then herself in a classroom at Louisiana Technical College in Baton Rouge.

Oct. 10, 2007: A 14-year-old student at a Cleveland (Ohio) high school, Asa H. Coon, shot and injured two students and two teachers before he shot and killed himself. The victims' injuries were not life-threatening.

April 16, 2007: A 23-year-old Virginia Tech student, Cho Seung-Hui, killed two in a dorm, then killed 30 more 2 hours later in a classroom building on the Blacksburg, Va., campus. His suicide brought the death toll to 33, making the shooting rampage the most deadly in U.S. history. Fifteen others were wounded.

Feb. 12, 2007: Sule­j­man Talovic, 18, wear­ing a trench­coat and car­ry­ing a shot­gun, sprays a pop­u­lar Salt Lake City shop­ping mall, killing five people and wound­ing four oth­ers. Talovic is killed in a gunfire exchange with police.

Oct. 3, 2006: 32-year-old Carl Charles Roberts IV entered the one-room West Nickel Mines Amish School in Nickel Mines, Pa., and shot 10 schoolgirls, ranging in age from 6 to 13 years old, and then himself. Five of the girls and Roberts died.

Sept. 27, 2006: Adult male held six students hostage at Platte Canyon High School in Bailey, Colo., and then shot and killed Emily Keyes, 16, and himself.

Aug. 24, 2006: Christopher Williams, 27, looking for his ex-girlfriend at Essex Elementary School in Essex, Vt., shot two teachers, killing one and wounding another. Before going to the school, he had killed the ex-girlfriend's mother.

Nov. 8, 2005: One 15-year-old shot and killed an assistant principal at Campbell County High School in Jacksboro, Tenn., and seriously wounded two other administrators.

March 21, 2005: Jeff Weise, 16, killed grandfather and companion, then arrived at school where he killed a teacher, a security guard, 5 students, and finally himself, leaving a total of 10 dead in Red Lake, Minn.

Sept. 24, 2003: Two students are killed at Rocori High School in Cold Spring, Minn., by John Jason McLaughlin, 15.

July 8, 2003: Doug Wil­li­ams, 48, a pro­duc­tion as­sembly­man for 19 years at Lock­heed Mar­tin Aero­naut­ics Co., goes on a ram­page at the de­fense plant, fatally shoot­ing five and wound­ing nine be­fore tak­ing his own life with a shot­gun.

April 14, 2003: One 15-year-old killed, and three students were wounded at John McDonogh High School in New Orleans by gunfire from four teenagers (none were students at the school). The motive was reportedly gang-related.

October 2002:  A series of sniper-style shootings leave 10 dead around the Washington, D.C., area.

Oct. 28, 2002: Robert S. Flores Jr., 41, a student at the nursing school at the University of Arizona in Tucson, shot and killed three female professors and then himself.

March 22, 2001:  One teacher and three students wounded by Jason Hoffman, 18, at Granite Hills (Calif.) High School. A policeman shot and wounded Hoffman.

March 5, 2001:  Two killed and 13 wounded by Charles Andrew Williams, 15, firing from a bathroom at Santana High School in Santee, Calif.

Dec. 26, 2000: Mi­chael Mc­Der­mott, a 42-year-old soft­ware test­er shoots and kills sev­en co-work­ers at the In­ter­net con­sult­ing firm where he is em­ployed.

May 26, 2000: One teacher, Barry Grunow, shot and killed at Lake Worth Middle School by Nate Brazill, 13, with .25-caliber semiautomatic pistol on the last day of classes in Lake Worth, Fla.

March 10, 2000: Two students killed by Darrell Ingram, 19, while leaving a dance sponsored by Beach High School in Savannah, Ga.

Sept. 16, 1999:  A gunman, identified as as Larry Gene Ashbrook, opened fire at a prayer service in Fort Worth, Texas, killing six people before committing suicide.

July 1999: A stock exchange trader in Atlanta, killed 12 people including his wife and two children before taking his own life.

April 20, 1999: Eric Har­ris and Dylan Kle­bold, stu­dents at Columbine High, open fire at the Littleton, Colo., school, killing a dozen stu­dents and a teach­er and caus­ing in­jury to two dozen oth­ers be­fore tak­ing their own lives.

Dec. 1, 1997: Michael Carneal opened fire with a .22-caliber pistol in the lobby of Heath High School in Paducah, Ky., shooting eight teenagers during their morning prayer circle meeting. Three students were killed, five others were wounded.

March 24, 1998: Middle school stu­dents Mitchell John­son and An­drew Golden pull a fire alarm at their school in a small rur­al Arkan­sas com­munity and then open fire on stu­dents and teach­ers. Four stu­dents and a teach­er who tried shield the chil­dren are killed and 10 oth­ers are in­jured. Be­cause of their ages, Mitchell. 13, and An­drew, 11, are sen­tenced to con­fine­ment in a ju­ven­ile fa­cil­ity un­til they turn 21.

July 1, 1993: Gi­an Luigi Ferri, 55, kills eight people in an of­fice build­ing in San Fran­cisco's fin­an­cial dis­trict. Six more were injured before Ferri turned the gun on himself when confronted by police.

Nov. 1, 1991: Gang Lu, a gradu­ate stu­dent in phys­ics from China, shoots four people to death at the Uni­versity of Iowa. Lu, who took his own life in the in­cid­ent, was up­set about not get­ting an aca­dem­ic hon­or.  Two oth­ers were crit­ic­ally wounded.

Oct. 16, 1991: Twenty-three were killed and 20 more are wounded in Killeen, Texas, after George Jo Hennard, 35, crashes his pickup truck in­to a Luby's cafet­er­ia crowded with lunch­time pat­rons and be­gins fir­ing in­dis­crim­in­ately with a semi­auto­mat­ic pis­tol. Hennard is later found dead of a gun­shot wound in a res­taur­ant re­stroom.

April 27, 1979:  A sniper killed two and injured more than 50 spectators gathered to watch the Battle of Flowers Parade during the annual Fiesta celebration in San Antonio, Texas.

Aug. 1, 1966: A University of Texas engineering student and former Marine, Charles Joseph Whitman, fired at random targets from the 28th floor observation deck of the Main Building, killing 13 and wounding 32 others, before being shot and killed by an Austin, Texas, police officer.