At least ten people, one of them a policeman, were killed by a gunmen who opened fire Monday in a grocery store in Boulder, Colorado, according to police.

The identities of the victims were not revealed, except for the identity of the dead policeman named Eric Talley, 51. 

Maris Herold, chief of police for the city below the Rocky Mountains, said, 10 people were killed at the scene, including one of our officers ... the next policeman who answered the distress call - he was the first to arrive at the scene - and was killed as a result of being shot." 

According to the authorities, a gunman opened fire on Monday afternoon in a supermarket called King Supers in the city, located 50 km from Denver, the state capital, before police arrested him.

- 'A horrific and horrific crime' -

"Today, Boulder witnessed a horrific and horrific mass murder," County Prosecutor Michael Dougherty said.

He added that the police arrested a suspect who was injured during his arrest.

The public prosecutor promised to bring "justice" to all the victims, describing them as "people who were living their lives, who were shopping, before the gunman tragically destroyed their lives."

Footage broadcast live by an eyewitness showed at least one person being arrested. The man, who was wearing only sweatpants, appeared to be white and middle age and had light injuries to his leg that had traces of blood, while his hands were cuffed behind his back and the police took him outside the store.

The police did not identify the suspect nor provide any details about the motives for his attack.

According to American media, the gunman fired from an AR-15 machine gun, a very common weapon in the United States and used by a large amount of the perpetrators of mass killing operations in the United States.

It is expected that the investigation into this attack will be long and complicated, and the work of criminal investigation teams at the shooting site is expected to continue for several days.

In Washington, White House spokeswoman Jen Psaki said that President Joe Biden was informed of what happened in Boulder.

About half an hour after the first round of gunfire, dozens of police officers were surrounding the supermarket, supported by armored vehicles.

Then a few heavily armed policemen climbed onto the roof of the supermarket with a fire truck's ladder.

Eyewitnesses who were inside the store when the shooting started shortly before 3 pm (21:00 GMT) stated that they heard many gunshots before they managed to escape through a back exit.

For his part, the city's police chief, Kerry Yamaguchi, announced that his officers arrived at the site minutes after receiving the report, stressing that they managed to enter the building "very quickly."

Several customers who were hiding in the store said that the police had rescued them.

- Arms sale laws -

Such shootings are common in the United States and often occur in schools, malls, or places of worship.

Successive administrations have failed to stop or even limit these killings.

In mid-February, President Biden called on Congress to act "immediately" to reform the nation's firearms legislation.

The Democratic President’s call came on the occasion of the third anniversary of the massacre in a high school in Parkland, Florida, which killed 17 people.

On Monday evening, Senate Democratic Majority Leader Chuck Schumer said in a tweet commenting on the Boulder attack that "the Senate should push this legislation forward to help stop the epidemic of gun violence, and it will."