US police officer killed in mass Colorado shooting remembered as lovable father of seven

A Boulder police officer has been named among 10 people killed in a supermarket shooting in Colorado.

Officer Eric Talley was slain after being first on scene at the King Soopers store after responding to reports of a gunman inside.

The alleged gunman, who was injured during the shooting, is now in custody.

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The suspect is being treated at hospital.

Homer, Mr Talley's father, told US networks his son was funny and lovable.

"He had a great sense of humor, he was a prankster," Homer Talley said.

"He loved his family more than anything."

Mr Talley was the father of seven children and was training to become a drone operator because he believed it to be safer than a police officer on the street.

Officers had escorted a shirtless man with blood running down his leg out of the store in handcuffs but authorities would not say if he was the suspect.

Police said they will not release names of other victims until families have been notified.

"We will work around the clock to get this accomplished," Boulder's police chief said.

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Police still do not have a motive for the shooting at the store in Boulder, which is about 40 kilometres northwest of Denver and home to the University of Colorado.

Video taken by an eyewitness to the shooting appears to show people lying on the ground inside and outside the store, and purported gunshots are heard.

The video, taken by Dean Schiller, is part of a longer live stream that he took as the shooting progressed and police arrived.

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In the excerpt, Mr Schiller is heard calling out saying people need to call 911.

"We don't know if there's a shooter — active shooter, active shooter somewhere," he said in the video.

Mr Schiller is heard asking what appears to be a store employee whether a shooter went into the store.

Ryan Borowski, one of the people inside the grocery store when a shooter starting firing shots, said everyone helped each other get out of the back of the store.

He said he heard two loud sounds, and by the third one, he and the people around him realised they were gunshots. He said they started running to the back of the store and employees helped them out the back door.

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Television helicopter video showed law enforcement vehicles and officers massing outside, including SWAT teams, and at least three helicopters on the roof of the store.

Officers had their guns drawn, and some windows at the front of the store were broken.

Authorities over a loudspeaker said the building was surrounded and that “you need to surrender."

They said to come out with hands up and unarmed.

A man who said he was shopping at the store told KCNC-TV he heard a loud bang, then heard another, and by the third, everyone was running.

He said they ran to the back of the store, found the employee area and workers told them how to escape.

He said they walked single file, with their arms on the backs of those in front of them.

Officers were helping people out of the store to safety.

A person who answered the telephone at a nearby sandwich shop said he and his employees were locked down in the back of the store and all were safe.

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Someone who answered the phone at nail studio next door said she and her colleagues were safe.

Neither had details on what happened at the market across the street.

With Associated Press and CNN