Two Americans arrested in connection with the death of an Italian paramilitary officer had blamed each other for committing murder, court documents sent to reporters show.

Gabriel Christian Natale-Hjorth, 18, and Finnegan Lee Elder, 19, both from Mill Valley, California, were detained by police in Rome on Friday for alleged homicide and attempted extortion.

Police have said the pair had a violent encounter with two plainclothes members of the storied Carabinieri paramilitary corps, after having stolen a backpack from Italian national and demanded money and a gram of cocaine in exchange for its return.

On Sunday, police released audio files of two calls with the Italian national who allegedly had his backpack stolen. He alleged he had spoken to the people who stole his bag by calling his cellphone, which had been inside the bag, adding that the suspects demanded money for the return of his belongings.

The dispatcher agreed to send an officer to meet the victim.

Mario Cerciello Rega, 35, who had just returned to duty a few days earlier from his honeymoon, was dispatched on Friday to meet with the Americans as part of the investigation, authorities said.

A detention order says Natale-Hjorth, who can understand Italian, confirmed that Rega identified himself as a Carabiniere officer. Elder, who doesn't speak the language, denies the officer revealed who he was.

The encounter quickly turned deadly with a violent struggle that resulted in Rega's stabbing. The pair then fled to their hotel room at the four-star Le Meridien, where police found them hours later, the order says.

When separately interrogated, each suspect blamed the other for the stabbing, according to the document. However, Elder had recognized the weapon — a large knife seized from their hotel room — as his own and also confirmed it was the murder weapon, the document says.

A leaked photo that appears to show one of the men in police custody, blindfolded and handcuffed while sitting with his head bowed, is being investigated by police. Police have not denied its authenticity.

Italy's Deputy Prime Minister Matteo Salvini tweeted that anyone concerned about the treatment of those arrested should remember the only real victim is the officer who died. He added that if the suspects are found guilty, they deserve life in prison.

Elder's family issued a statement Sunday saying that they had not been able to contact their son.

"We are shocked and dismayed at the events that have been reported, but have very little independent information about these events," they said, adding they shared condolences for the police officer's family and community. "Our thoughts are with all of those who have been impacted by this tragedy."

The detention order requires the men to be detained in isolation and forbids them from meeting. It also deems them a flight risk because they are foreign citizens.

Rega is expected to be buried on Monday after a public viewing is held on Sunday. It is unclear when the next court hearing will be scheduled.