BY: EMILY SHAPIRO, IVAN PEREIRA AND JEFFREY COOK, ABC NEWS

(BOULDER, Colo.) — Multiple people were killed, including a police officer, after a suspect opened fire at a King Soopers grocery store in Boulder, Colorado, Monday afternoon, police said.

A person of interest, who was wounded during the incident, was taken into custody, they confirmed.

A law enforcement source told ABC News officers initially responded to a report of someone being shot in the parking lot, and when they arrived at the scene, a suspect opened fire on them.

Several other law enforcement agencies quickly arrived at the scene, including the state SWAT team.

The Boulder Police Department took to Twitter at 2:49 p.m. local time to warn residents of an “active shooter” and telling them to stay away from the area.

ALERT: Active Shooter at the King Soopers on Table Mesa. AVOID THE AREA. PIO is en-route.

— Boulder Police Dept. (@boulderpolice) March 22, 2021

Then, at 7:10 p.m. EST, they tweeted out an alert asking people about three miles from the shopping center “to shelter in place” while officers responded to a report of an “armed, dangerous individual.”

The order was lifted around 8:41 p.m.

“PD is investigating to determine if this is related to King Soopers shooting,” the police department wrote.

Eyewitnesses shared videos from the parking lot of the store on social media. The videos show officers ordering a suspect to come out of the store with his hands up and surrender.

Inside the store, shoppers and employees were seen trying to flee or hide.

The suspect was allegedly carrying a long gun, law enforcement sources told ABC News.

Andy Arellano, a store employee, told ABC affiliate KMGH he was concerned for his co-workers and shoppers as shots rang out.

“We were like sitting ducks, you know, and that’s one thing that I’m reliving it and looking at it in my head. And that, that bothers me, I’m still shivering, I’m still shaking,” he said.

Eyewitness Andrew Hummel told KMGH he was at a store when he heard the gunshots and ran out of the shopping center with others.

“Everybody kind of sprinted toward the back of the store,” Hummel told the station.

Hummel said his roommate, who works at the store where the shooting happened, went to a storage room and hid there with some customers, texting Hummel and others updates.

“Yeah, I think one of the biggest scary text[s] that he sent he just said, ‘I love you guys, like thank you for everything, in case, like, things go bad,"” Hummel said. “That was a really hard text … that’s something that I would never want to hear from any of my friends because I knew the seriousness of what was going on and I was horrified. It was truly horrifying.”

Sarah Moonshadow, another eyewitness, told the station she was in the supermarket with her son when she heard four gunshots.

“We were hiding down, kind of in the self-checkout area, and I just knew like this is a problem, and I started counting in between shots and then I just grabbed Nicholas, I said, ‘Move now."”

President Joe Biden has been briefed about the shooting, White House press secretary Jen Psaki said Monday night.

Attorney General Merrick Garland has also been briefed, a Department of Justice official told ABC News.

Colorado Gov. Jared Polis tweeted out a statement Monday afternoon reacting to the shooting.

“Like my fellow Coloradans, I am closely watching unfolding events at King Soopers in Boulder,” he wrote. “My prayers are with our fellow Coloradans in this time of sadness and grief as we learn more about the extent of the tragedy.”

In another statement later Monday evening, Polis asked for residents to have patience as the investigation continues.

“Right now, the biggest priority is to let local law enforcement and the City of Boulder to do their work to ensure the safety of those involved,” he said.

Kroger, the parent company of King Soopers, released a statement expressing their condolences and sympathies to their associates and customers and thanking the “first responders who so bravely responded to this tragic situation.” They also said they are cooperating with investigators.

United Food and Commercial Workers International Union, the union that represents the store workers, said on Twitter Monday night that they are also monitoring the situation.

This is a developing story. Please check back for updates.

ABC News’ Luke Barr and Alexander Malin contributed to this report.

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