Factbox: Major shootings in the United States

If the death toll is not revised lower, it would be the deadliest mass shooting in modern U.S. history and among a series of such incidents dating back to at least the mid-1990s.

Below are some of the bloodiest episodes in recent years, ranked by the number of dead:

ORLANDO, June 12, 2016 - A gunman fatally shoots 49 people at gay nightclub Pulse before he is shot dead by police. At the time it was the worst mass shooting in recent U.S. history.

VIRGINIA TECH, April 16, 2007 - A gunman slaughters 32 people and kills himself at Virginia Tech, a university in Blacksburg, Virginia.

SANDY HOOK, Dec. 14, 2012 - A man shoots dead his mother, then kills 20 children, six adults and himself at Sandy Hook Elementary School in Newtown, Connecticut.

SAN BERNARDINO, Dec. 2, 2015 - A husband and wife kill 14 people at a workplace holiday party in San Bernardino in Southern California before dying in a shootout with police.

COLUMBINE, April 20, 1999 - Two teenagers rampage through Columbine High School in Littleton, Colorado, shooting dead 12 students and a teacher and wounding more than 20 others before killing themselves.

BINGHAMTON, April 3, 2009 - A Vietnamese immigrant opens fire at an immigrant services center in Binghamton, New York, killing 13 people and wounding four. He then kills himself.

FORT HOOD, Nov. 5, 2009 - An army major and psychiatrist opens fire at Fort Hood, a U.S. Army base in Texas, killing 13 people. He is sentenced to death.

WASHINGTON, D.C., Sept. 16, 2013 - A former Navy reservist working as a government contractor kills 12 people at the Washington Navy Yard. He is shot dead by police.

COLORADO, July 20, 2012 - A masked gunman kills 12 people and wounds 70 when he opens fire at a midnight premiere of Batman film "The Dark Knight Rises" in Aurora, Denver. He receives a life sentence.

WASHINGTON, D.C., October 2002 - Two men ambush 13 people, killing 10 of them, in sniper-style shootings that terrorize the Washington area for three weeks. One sniper was executed and the other was sentenced to life in prison.

OREGON, Oct. 1, 2015 - A man opens fire on the Umpqua Community College campus in southwest Oregon, killing nine people before he is shot dead by police.

CHARLESTON, June 17, 2015 - A white supremacist kills nine black churchgoers at a historic, predominantly black church in Charleston, South Carolina.

WACO, May 17, 2015 - Rival motorcycle gangs kill nine at a restaurant in Waco, Texas. More than 170 people are arrested.

WISCONSIN, Aug. 5, 2012 - A white supremacist kills six worshippers in a Sikh temple in Oak Creek, Wisconsin. The gunman kills himself.

TUCSON, Jan. 8, 2011 - Then-U.S. Representative Gabrielle Giffords is the target of an assassination attempt by a gunman in Tucson, Arizona. Six people are killed and 13, including Giffords, are wounded.

ISLA VISTA, May 23, 2014 - A college student killed six people, three in his apartment and others on the streets of this small California town. The mentally ill gunman committed suicide.

AMISH school, Oct. 2, 2006 - A gunman kills five girls in a one-room Amish schoolhouse in Nickel Mines, Pennsylvania, before killing himself.

DALLAS, July 7, 2016 - A U.S. military veteran killed five police officers and wounded seven more in the deadliest attack on police. The suspect was killed by a police bomb.

(Compiled by Jeff Benkoe and Jonathan Oatis; Editing by Susan Thomas and Andrew Hay)