A mass shooting on Monday at a supermarket in Boulder, Colorado, left 10 people dead, including the first police officer to arrive on the scene, and a suspect injured in the violence was arrested, authorities told a news conference hours later.
Police gave few immediate details of the shooting and no known motive for the violence, which unfolded at about 3 pm at a King Soopers grocery store in the Table Mesa area of Boulder, a city at the eastern foot of the Rockies about 28 miles (45 km) northwest of Denver, Reuters reported.
The bloodshed marked the second deadly US mass shooting in a week, following gun violence last Tuesday that left eight people dead, including six Asian women, at three locations in and around Atlanta. A 21-year-old man has been charged with those killings.
Boulder Police Chief Maris Herold said 10 people perished in the attack at King Soopers grocery. Among them were 51-year-old police officer Eric Talley, who she said was the first to respond to the shooting, about 2 miles from the University of Colorado's flagship campus.
Police said the suspected gunman, who was arrested, was believed to be the only individual with serious injuries who survived the bloodshed.
At a news conference, Boulder Police Department Commander Kerry Yamaguchi said "We had a very tragic incident today here at the King Soopers."
Quick response from law enforcement from around the area saved lives, CNN reports quoting him.
Kerry Yamaguchi said there is now no ongoing threat related to the shooting, saying "a person of interest in custody."
"I can share with the public today, or this evening, that there is no ongoing public threat," he added.
A Boulder Community Health spokesman, Rich Sheehan, said one person taken by ambulance to the hospital from the supermarket was undergoing medical treatment, but Sheehan declined to describe the nature of injuries or the patient's condition.
Dean Schiller, who described himself as a journalist and who was live-streaming footage from the scene for a YouTube channel identified as ZFG Videography, said in interviews with local media he heard what sounded like gunshots as he exited the grocery store. Schiller also said he saw three apparent shooting victims but had no information about their conditions.
A short time later in a parking lot outside the store, Schiller said, he saw police officers surround a sport utility vehicle as they ordered its occupants to come out.
TV news footage showed police leading customers and workers out of the store with hands on their heads. Aerial footage also showed a heavy law enforcement presence outside the supermarket, along with at least two ambulances.
Table Mesa is home to the hilltop laboratory of the National Center for Atmospheric Research. The supermarket is located about 2 miles from the University of Colorado's flagship campus.
Colorado Governor Jared Polis said on Twitter he was monitoring events unfolding in Boulder, adding, "My prayers are with our fellow Coloradans in this time of sadness and grief as we learn more about the extent of the tragedy."
The FBI said on Twitter that its agents were assisting local police in the investigation of the supermarket shooting.