Backgrounder: U.S. major shooting incidents during Obama's administration

More than 57,000 incidents of gun violence happened in the United States in 2016, killing at least 14,000 people and injuring 30,000, according to non-profit corporation Gun Violence Archive.

The following are major shooting cases in the United State under President Barack Obama's eight-year tenure.

-- HOUSTON, July 7, 2016 -- Four police officers were killed and seven others injured as two snipers opened fire during a protest against police shootings across the United States.

-- ORLANDO, June 12, 2016 -- A gunman wielding an assault-type rife and a handgun killed at least 50 people at a gay nightclub in Orlando in the worst mass shooting in U.S. history. Obama decried the tragedy as an "act of terror."

-- SAN BERNARDINO, Dec. 2, 2015 -- At least 14 people were killed and 17 others were injured after gunmen opened fire at a social services center in San Bernardino City, Southern California.

-- OREGON, Oct. 2, 2015 -- At least 10 people, including the gunman himself, died in a shooting at a community college in the state of Oregon.

The gunman, identified by U.S. media as 26-year-old Chris Harper Mercer, opened fire at Umpqua Community College in Roseburg, about 290 km south of Portland, Oregon's largest city.

-- CHARLESTON, June 17, 2015 -- A white man opened fire during a prayer meeting inside a historic black church in downtown Charleston, killing nine people in an assault that authorities described as a hate crime.

-- CHICAGO, May 26, 2015 -- Twelve people were killed and more than 40 more wounded in shootings in Chicago during Memorial Day.

-- TEXAS, May 17, 2015 -- Nine people were killed and several wounded after a shootout between rival biker gangs in Waco, Texas, with more gangs threatening to descend onto the town after the violence.

-- WASHINGTON, Sept. 17, 2013 -- A shooting inside a building at the Washington Navy Yard that serves as the headquarters of the Naval Sea System Command killed 13 people, including a suspect later identified by the FBI as 34-year-old navy contractor employee Aaron Alexis.

-- NEWTOWN, Dec. 14, 2012 -- A shooting incident in an elementary school in Newtown, Connecticut killed 20 children and six adults.

-- CHICAGO, Aug. 5, 2012 -- At least seven people were killed in a shooting incident at a Sikh temple in Oak Creek, in the state of Wisconsin.

-- AURORA, Colorado, July 20, 2012 -- Twelve people were killed and 59 others injured at a Batman movie premier, where a lone, heavily armed gunman burst into a packed theater in a suburb 10 miles east of Denver.

Obama called the act "mindless, evil, senseless." Local police identified the perpetrator as James Holmes, 24.

-- TUSCON, January 9, 2011 -- A gunman opened fire at a public gathering outside a grocery in Tuscon, Arizona, killing six people including a nine-year-old girl and wounding at least 12 others. Congresswoman Gabrielle Giffords was severely injured with a gunshot to the head.

-- FORT HOOD, November 6, 2009 -- U.S. army psychologist Major Nidal Hasan opened fire at a military base in Fort Hood, Texas, leaving 13 dead and 42 others wounded.

-- BINGHAMTON, April 4, 2009 -- A man shot dead 13 people at a civic center in Binghamton, New York.

-- NORTH CAROLINA, March 30, 2009 -- A heavily-armed gunman shot dead eight people, many of them elderly and sick, in a private-owned nursing home in North Carolina.

-- DEKALB, February 15, 2008 -- A man opened fire in a lecture hall at Northern Illinois University in DeKalb killing five students and wounding 16 others before laying down his weapon and surrendering. Endi