Updated

Witnesses who were inside the King Soopers grocery store in Boulder, Colo., on Monday during the mass shooting described a chaotic scene after a man walked into the store armed with some kind of rifle, and without saying a word, opened fire.

The Denver Post spoke to one witness who wished to remain anonymous. The witness said he was with a roommate about to leave the store when they spotted the gunman.

"He just came in and started shooting," the witness told the paper. The roommate told the paper that the shooting seemed to be methodic. "He wasn’t spraying."

Investigators in Boulder were trying to learn more about the suspect and any motive but provided the media with some new details during a late news conference Monday. They said 10 people were killed, including a veteran police officer who was one of the first to arrive at the scene.

The suspect was in custody and hospitalized due to an injury.

One witness, who identified himself with his first name, David, told a reporter with Fox 31 Denver he was picking up sushi at the store and heard the gunshots ring out.

"I knew every gunshot that was shot went into somebody," he said. "I could hear... I could tell when a gunshot doesn’t ricochet, but I also can tell when a gunshot goes into somebody."

A witness told The Associated Press he had just left the supermarket when he heard gunshots and saw three people lying face down, two in the parking lot and one near the doorway. He said he "couldn't tell if they were breathing."

Video posted on YouTube showed one person on the floor inside the store and two more outside on the ground. What sounds like two gunshots are also heard at the beginning of the video.

James Bentz told the Post that he was in the back of the store when the shooting started. He described the scene like a "stampede" of people looking for an exit. He told the paper that some younger people helped older shoppers out of the store and to safety.

He said that he thought of other notorious shootings in the state, like Columbine.

"It seemed like all of us had imagined we’d be in a situation like this at some point in our lives," he said.

The Associated Press contributed to this report.