Umpqua Community College alumnus Donice Smith (L) is embraced after she said one of her former teachers was shot dead, near the site of a mass shooting at Umpqua Community College in Roseburg,Oregon October 1, 2015. A gunman opened fire at a community college in southern Oregon on Thursday, killing 13 people and wounding some 20 others before he was shot to death by police, state and county officials said, in the latest mass killing to rock a U.S. school. There were conflicting reports on the number of dead and wounded in the shooting rampage in Roseburg, which began shortly after 10:30 a.m. local time (1730 GMT).

Police guard the site of a mass shooting at a bar in Thousand Oaks, California, U.S. November 8, 2018.

Police forensics investigators work at the crime scene of a mass shooting at the Pulse gay night club in Orlando, Florida, U.S. June 12, 2016.

Police officers guard the Tree of Life synagogue following shooting at the synagogue in Pittsburgh, Pennsylvania, U.S., October 27, 2018.

Aaron Alexis moves through the hallways of Building #197 carrying a Remington 870 shotgun in this undated handout photo released by the FBI. Over the course of an hour-long shooting incident at the Washington Navy Yard in Washington, DC on September 16, 2013, Aaron Alexis killed 12 people and wounded four others before he was shot and killed by law enforcement officers. REUTERS/FBI/Handout via Reuters

Shoes are piled in the rear of Ned Peppers Bar at the scene after a mass shooting in Dayton, Ohio, U.S. August 4, 2019.

Investigators work at one scene of a shooting spree in downtown Samson, Alabama March 10, 2009. At least 10 people including the suspected gunman and his mother were killed in the shooting spree and car chase in southern Alabama on Tuesday, authorities said.

United States Army Specialist Robert Orcutt prays near a makeshift memorial for victims of the shootings at Fort Hood Army post in Fort Hood, Texas November 9, 2009. The death toll from an Army psychiatrist who opened fire at the Fort Hood Army post rose to 13 on Friday, and Army officials said the suspected shooter was hospitalized and on a ventilator. U.S. intelligence agencies learned an Army psychiatrist tried to contact people linked to al Qaeda and they gave the information to federal authorities before the man allegedly went on shooting spree in Texas last week, U.S. sources said on Monday.

Police enter Norris Hall at Virginia Tech in Blacksburg, Virginia, April 17, 2007. The gunman who killed 32 people and then himself at Virginia Tech university on Monday was identified by police on Tuesday as Cho Seung-Hui, a South Korean studying at the university. Police said he was 23 and that one of two guns recovered was used in both of the two separate shooting incidents at the campus on Monday.

People gather at a makeshift memorial left in memory of the victims killed in a shooting at Santa Fe High School in Santa Fe, Texas, U.S., May 21, 2018.

Adin Chistian (16), student of the Marjory Stoneman Douglas High School, embraces his mother Denyse, next to the crosses and Stars of David placed in front of the fence of the school to commemorate the victims of a shooting, in Parkland, Florida, U.S., February 19, 2018.

Two teenagers rampaged through Columbine High School in Jefferson County, Colorado, fatally shooting 12 students and a teacher and wounding more than 20 others before killing themselves. REUTERS

Law enforcement officers surround the car which John Allen Muhammad and John Lee Malvo were in when police arrested them at a rest stop near Myersville, Marylan October 24, 2002. Former U.S. soldier John Allen Muhammad, a Gulf War veteran, and John Lee Malvo, his 17-year-old step-son were arrested at the rest stop in rural Maryland early Thursday in the hunt for culprits in 10 sniper-style slayings in the Washington, D.C., area.

People pray in the First Baptist Church of Sutherland Springs where 26 people were killed in a shooting attack last week, as the church was opened to the public as a memorial to those killed, in Sutherland Springs, Texas, U.S. November 12, 2017.

Police is seen after a mass shooting at a Walmart in El Paso, Texas, U.S. August 3, 2019.

A pair of cowboy boots is shown in the street outside the concert venue after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. October 1, 2017. REUTERS/Las Vegas Sun/Steve Marcus

Waco Police investigators are at the scene of shooting at the Twin Peaks Restaurant in Waco, Texas May 18, 2015. Police worried about retaliation attacks after 170 people were charged on Monday in connection with Sunday's shootout between motorcycle gangs that left nine dead and 18 wounded at a Waco, Texas, restaurant turned into a blood-soaked shambles.

The American Civic Association building is seen April 4, 2009 after Binghamton, New York Police reopened Front Street to traffic. Gunman Jiverly Wong, 41, went on a shooting spree on Friday killing 13 people before committing suicide inside the building.

First-grader Henry Terifay and his sister, fourth-grader Kelly Terifay, wait outside Sandy Hook Elementary School after a shooting in Newtown, Connecticut, December 14, 2012. A shooter opened fire at the elementary school.

People gather outside Emanuel African Methodist Episcopal Church after the street was re-opened a day after a mass shooting left nine dead during a bible study at the church in Charleston, South Carolina June 18, 2015. A 21-year-old white gunman accused of killing nine people at a historic church was arrested on Thursday, said U.S. officials, who are investigating the attack as a hate crime.

A resident places flowers at a makeshift memorial outside a municipal government building where a shooting incident occurred in Virginia Beach, Virginia, U.S. June 1, 2019.