A school shooting in a Washington state high school on Friday ended with two people, including the suspect, dead, and at least four others wounded.
In a separate incident, also on Friday, a gunman killed two police officers and wounded two others in California. The suspect has been apprehended.
The latest two incidents were the latest in a long string of shooting rampages in the United States. We look at some of the most notable since the turn of the decade:
Feb 12, 2010: Harvard-trained biology professor Amy Bishop, 42, opened fire during a faculty meeting at the University of Alabama in Huntsville, killing three colleagues and injuring three others. She was sentenced to life in prison without parole in 2012.
Jan 8, 2011: A gunman opened fire at Congresswoman Gabrielle Giffords and other bystanders outside a supermarket in Tucson, Arizona. Ms Giffords was shot in the head but miraculously survived the attack. Six people, including a federal judge and a nine-year-old girl. were killed and 12 others wounded.
Oct 12, 2011: A man killed his ex-wife and seven others in a shooting at a hair salon in Seal Beach, California. Scott Evans Dekraai, 41, was armed with three guns and was wearing body armour. He was arrested while trying to leave the scene.
April 2, 2012: A gunman killed seven people and wounded three at a Christian college in Oakland, California. Forty-three-year-old Korean-American One Goh, a former student of the college, was arrested.
July 20, 2012: A masked gunman killed 12 people and wounded 58 others when he opened fire on moviegoers at a showing of the Batman film, The Dark Knight Rises, in Aurora, a suburb of Denver. The suspect, 24-year-old James Holmes, was a student of the University of Colorado.
Aug 5, 2012: A former soldier named Wade Michael Page, 40, opened fire and killed six people during Sunday service at a Sikh temple in Oak Creek, Wisconsin, before he was shot dead by a police officer.
The reasons for his attack remain unclear, although investigators have learnt that he was a member of two heavy metal bands, Definite Hate and End Apathy, which had white-supremacist views.
Dec 11, 2012: A masked gunman opened fire inside an Oregon shopping mall, killing two people and wounding one. He then turned the gun on himself.
Dec 14, 2012: A man wielding a military-style rifle and powerful handguns killed 20 children and seven adults in Newton, Connecticut. The 20-year-old, Adam Lanza, shot his mother Nancy dead at home, before driving to Sandy Hook Elementary School.
There, he opened fire and killed 12 girls and eight boys aged six and seven. Also killed were five teachers and the school principal, some of whom had died while trying to shield the children. After the 10-minute rampage, Lanza shot himself.
June 7, 2013: After killing his father and brother at home, 23-year-old John Zawahri strode across Santa Monica, California, firing at people, cars, a public bus and buildings before being shot and killed by the police at the Santa Monica College Library.
He killed five people in total, and wounded four others.
Dec 13, 2013: Karl Halverson Pierson, 18, stormed Arapahoe High School in Colorado armed with a shotgun and Molotov cocktails and shot two students before killing himself. The shooter had shouted that he was looking for a particular teacher, in what police said was a planned revenge attack.
One of the victims, Claire Davis, 17, was shot point-blank in the face, and died after eight days on life support.
May 23, 2014: The son of a Hollywood director and a Malaysian mother killed six people and injured 13 others in a bustling Californian college town.
Elliot Rodger, 22, fatally stabbed three flatmates before going on a shooting rampage in his black BMW, during which he killed two women outside a sorority house and a man in a deli.
After a gun battle with police, he was found dead with what is believed to be a self-inflicted gunshot wound to the head.
Rodger wrote a 140-page manifesto, My Twisted World, outlining his homicidal plans and published the unsettling document before beginning his rampage.
Sources: The Straits Times, Reuters, Bloomberg, AP, AFP, CNN, New York Times, Los Angeles Times