Two gunmen have shot and killed two police officers, before killing a third person and then committing suicide in Las Vegas, US.
Police in the US city of Seattle has commended the bravery of a student for disarming a gunman who had already killed one person and wounded three more.
The man who killed six people and injured seven more in a series of drive-by shootings in Santa Barbara on Friday posted a YouTube video threatening to go on a killing spree just hours before the attack.
A soldier shot dead three colleagues and injured 16 others before killing himself at the Fort Hood US Army base in Texas
The FBI has released CCTV video footage of Washington Navy Yard shooter Aaron Alexis as he proceeded to kill twelve people and injure many more.