Authorities in Boulder, Colorado, alerted residents on Monday about the situation of an active sniper in a supermarket.
It was not immediately clear whether there were any casualties.
Live video outside the supermarket – a King Soopers south of downtown Boulder – showed SWAT vehicles and more than a dozen policemen in tactical and camouflage clothing entering the store. Some of the front windows appeared to have been broken.
At one point, a man in handcuffs can be seen leaving the store with the authorities. It was unclear whether the man, who had no shirt and blood running down his leg, was a suspect.
Several minutes later, a line of people who appeared to have entered the store could be seen leaving surrounded by police.
Colorado Governor Jared Polis said he was “watching the situation closely” and added that “prayers are with our fellow Colorads at this time of sadness and grief, as we learn more about the extent of the tragedy.”
Aerial footage of the NBC affiliate KUSA showed a large presence of police and emergency medical services outside the King Soopers store.
This is a developing story. Please check again for updates.