The National Rifle Association has again defended the right to gun ownership after ten people were killed in a US supermarket shootout.
SWAT teams and at least three helicopters were called to the Kings Sooper store in Boulder - about 28 miles north of central Denver - after reports of a man wearing tactical gear shooting a rifle inside.
Terrified shoppers and workers scrambled for safety while armed officers exchanged fire with the suspect.
Police officer Eric Talley, 51, ran to the store following the call - but was killed as he tried to stop the man. Nine other members of the public, mostly doing their grocery shopping, were also shot dead.
Ahmad Al Aliwi Alissa, a 21-year-old from Arvada, Colorado, has been charged with ten counts of murder. He is currently in hospital in a stable condition, police said, and is expected to be released and transported to Boulder County Jail later on Tuesday.
US President Joe Biden will speak about the shooting on Tuesday. He has directed that all flags at the White House be
flown at half mast.
The names of the ten victims, which officers said were aged between 20 and 65, were read out at a news conference in Boulder on Tuesday.
The attack was the seventh mass killing this year in the US, following last week's shooting that left eight people dead at three Atlanta-area massage businesses.
And just hours after the horror unfolded in Boulder, the NRA tweeted a photograph of the Second Amendment to the Constitution with the caption: "A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed."
Vice President Kamala Harris described the latest shooting as "absolutely baffling" and paid tribute to the victims who were "living their lives, not bothering anybody".
Investigators have started sorting through evidence and witness interviews and do not yet have details on a motive for the shooting.
Dean Schiller told the Associated Press he had just left the supermarket when he heard gunshots and saw three people lying face down, two in the car park and one near the doorway.
He said he "couldn't tell if they were breathing".
Video posted on YouTube showed one person on the floor inside the store and two more outside on the ground. What sounds like two gunshots are also heard at the beginning of the video.
Colorado Governor Jared Polis tweeted a statement that his "heart is breaking as we watch this unspeakable event unfold in our Boulder community".