More than frequently, the United States has been the scene of massacres, mostly committed by US citizens and in many cases in schools.

The 18 worst massacres recorded during this millennium left a toll of 307 fatalities.

These are the 21st century massacres in the United States.

59 fatalities and more than 400 wounded left the shooting allegedly featured by Stephen Paddock (64 years old) who, from the 32nd floor of a hotel, opened fire indiscriminately against a crowd of people attending the closing of the country music festival Route 91 Harvest, next to the Mandalay Bay Hotel of that city.

The alleged murderer committed suicide, police said.

49 people from the LGBT community were killed in the Orlando Pulse club, a gay nightclub, after Omar Saddiqui Mateen, 29, indiscriminately shot inside the facility. More than 50 people were injured.

The killer was shot down in a hostage-release operation, according to the official statement.

14 people were killed and more than 20 were injured after a couple unloaded the cartridges of their automatic weapons in the middle of the year-end holiday of County Health Department employees.

The killers, 28-year-old Syed Rizwan Farrok and his wife Tashfeen Malik, 29, were killed in an exchange with police.

9 people died the day Christopher Sean Harper-Mercer burst at school shooting. Security agents at the university shot down the killer.

21-year-old Dylann Roof killed 9 parishioners of the Emanuel African Methodist Episcopal Church. After his capture, the young assassin stated that he wanted to start a racial war. Roof is the first American to be sentenced to death for a hate crime in the United States.

12 people were killed in the naval port after 34-year-old Aaron Alexis opened fire on people on the scene. The authorities killed Alexis.

In one of the country's most painful massacres, 20 children under the age of 8 and six adults were killed at Sandy Hook Elementary School.

The killer, Adam Lanza, 20, killed himself after committing the cruel slaughter. Lanza killed his mother moments before the event.

12 people lost their lives, and 58 were injured when 24-year-old James E. Holmes activated his AR-15 rifle during the premiere of the movie Batman, the Night Knight at the City Theater.

Holmes was sentenced to life imprisonment in 2015.

8 people were killed during a shooting at Seal Beach's Meritage Hall carried out by 41-year-old Scott Evans Dekraai, who at the time of his capture carried three pistols: a 9mm Springfield, a Smith & Wesson .44 Magnum, and a Heckler & Koch. Four. Five.

Evans faces a life sentence. Last August 18, an Orange County judge ruled that the death penalty would not apply.

Omar Thornton, who was fired from the Hartford Distributors Company for unlawfully selling alcoholic beverages, murdered 8 of his coworkers. Thornton killed himself after committing the crime.

Christopher Speight, 39, killed 8 people in a residential neighborhood of the village.

Speight surrendered to the authorities and in 2013 was sentenced to life imprisonment.

13 people died and 32 others were injured after Maj. Nidal Hasan, an ex-psychiatrist from the United States Army, opened fire inside the Soldier Readiness Center.

On August 27, 2013, the veteran was sentenced to death. Hasan is awaiting the execution of his sentence in the military jail of Fort Leavenworth, Kansas.

13 immigrants were killed in a community center where they took English classes after Jiverly Wong, a Vietnamese immigrant and US citizen, opened fire in the classroom. Wong committed suicide after the attack.

Robert Stewart, 45, murdered 8 people, in a nursing home. Two years later, the murderer was sentenced to life imprisonment.

10 people died in a shooting carried out by Michael McLendon. Among the victims were his mother, his grandparents, an aunt and uncle. McLendon committed suicide after committing the multiple homicides.

Robert Hawkins, 19, killed 8 people at the town's mall. The young murderer took his life after committing the crime.

On Virginia Tech's campus, 32 people were killed in one of the most painful massacres in the country.

The murderer, Seung-Hui Cho, a 23-year-old student, committed suicide after the multiple homicide.

9 people lost their lives when Jeff Weise, a 16-year-old teenager, opened fire at the school's facilities. Five students, his grandfather, a teacher, a security officer and another adult were the fatal victims of the event. Weise ended up taking his own life.