At least seven people are believed to have been killed by a shooter at a supermarket in Boulder, Colorado, according to local media reports.
While police have not confirmed any deaths, Boulder authorities said in a tweet that the incident unfolded just before 3pm local time at a King Soopers grocery store.
There are reports of "multiple people down" and "multiple shooters inside" the store.
One video of the incident from YouTube shows two victims lying on the ground in the parking lot of the store.
At least one victim is seen lying on the floor inside the store just moments before more gunshots are heard. Local reports say one victim is a police officer.
Live video from the scene showed a shirtless man with blood running down his leg being escorted out of the store in handcuffs by two police officers.
Some journalists at the scene reported that the bloody man was the alleged shooter, but that has not been confirmed.
Television helicopter video showed police vehicles and officers massing outside, including SWAT teams, and at least three helicopters on the roof of the store in the southern part of the city of Boulder.
Armed officers surrounded the store, including some who went on to the roof of the building.
Lie is unfair
My partner was shot and killed at the grocery store in the shooting in Boulder today. He was one of the best cops and people I knew. I love you forever brother, sorry I wasn't by your side. I called off work today
Please Pray for his wife and kids RETWEET & FOLLOW
— Sgt. Garrett Wooten #Trump (@NormaWo39235161) March 22, 2021
UPDATE FROM #BOULDER: Reports of 7 deceased at a supermarket shooting in Boulder, Colorado. A bloodied, possible suspect was led to an ambulance in handcuffs. pic.twitter.com/OoOfyhnJzt
Officers had their guns drawn, and some windows at the front of the store were broken. Authorities over a loudspeaker said the building was surrounded and that "you need to surrender". They said to come out with hands up and unarmed.
An ambulance pulled away from the store, apparently carrying the bleeding man brought out of the store in handcuffs.
A witness told Fox News the man had a "short assault rifle" and started shooting in the car park.
Confirmed one active shooter inside the King Soopers supermarket in Boulder, Colorado. 6 to 7 people dead, one is a Police Officer. Multiple people shot and wounded. Bomb squad is on the scene. Prayers for all involved! š#Boulder#Colorado#ActiveShooterpic.twitter.com/uJX5xoRRXi
One man told KDVR that he was "terrified" and "in shock initially when we realised what was happening".
The man said he was on his to pick up coffee from King Soopers when the shooting started.
Through tears, he noted that "people my age, my generation are used to this".
A man who said he was shopping at the store told KCNC-TV that he heard a loud bang, then heard another, and by the third, everyone was running. He said they ran to the back of the store, found the employee area and workers told them how to escape. He said they walked single file, with their arms on the backs of those in front of them.
Colorado Governor Jared Polis tweeted that he's "closely watching unfolding events at King Soopers in Boulder. My prayers are with our fellow Coloradans in this time of sadness and grief as we learn more about the extent of the tragedy."