Update: Boulder police say 10 people dead including officer in mass shooting at grocery store

Update:This story includes information shared by the Boulder Police Department in news conferences.

Police in Boulder, Colorado, responded to an active shooter situation at a King Soopers grocery store on Monday, and later confirmed that 10 people, including an officer who was first to respond to the scene, were killed in the attack.

Police later confirmed that one suspect is in custody, but did not identify the person other than saying the alleged perpetrator was being treated at a hospital. A shirtless man was earlier led out of the building in handcuffs and appearing to have blood on one leg, but it is unclear if he is a suspect in the attack.

Investigators didn't have details on a motive for the shooting, the Associated Press reported.

What are the details?

The New York Times reported that a witness who "posted a live video from the scene shortly after the shooting began, said he heard about a dozen shots and saw three people who appeared to be wounded — two in the parking lot and one inside the supermarket."

The Boulder Police Department responded to the scene. The FBI announced in a tweet later, "At the request of the Boulder Police Department, FBI Denver personnel are assisting with an investigation into an active shooter situation at a King Soopers grocery store on Table Mesa Drive in Boulder."

Another man at the scene of the incident told KCNC-TV that his son-in-law and grandchildren were in the store when the shooting broke out, and that the suspect "shot the woman in front of them" in line at the pharmacy.

Ryan Borowsky, who was also in the store at the time of the shooting, told CNN that once the firing started:

"We told employees what was going on so everybody helped each other and we just ran to safety as quickly as we could. I didn't see the shooter. I saw terrified faces running towards me and that's when I turned and ran the other direction."

Boulder police held news conferences afterward, but provided few details saying that victims' families were still being notified. Officials did confirm multiple civilians and one police officer were killed.

What about the slain officer?

Police have not revealed the identities of any of the victims except for the murdered officer, who was the first on the scene: 51-year-old Eric Talley, who had been with the force since 2010, the Associated Press reported.

"He was by all accounts one of the outstanding officers of the Boulder Police Department, and his life was cut too short," Boulder County District Attorney Michael Dougherty said of Talley during a news conference.

"This is a tragedy and a nightmare for Boulder County," Dougherty said, the Associated Press reported. "These were people going about their day, doing their shopping. I promise the victims and the people of the state of Colorado that we will secure justice."