Rome -- A commander of Italy's Carabinieri police force said Tuesday that two American teens accused of murdering an Italian officer set upon the officer and his partner as soon as they approached the pair and identified themselves as law enforcement. Finnegan Lee Elder and Gabriel Christian Natale-Hjorth are facing charges of murder and extortion in the stabbing death of Mario Cerciello Rega. The murder charges carry possible life prison sentences.

Providing further detail of the events that unfolded in the Friday killing last week, Carabinieri Commander Francesco Gargano said officers Mario Cerciello Rega and Andrea Varriale "were attacked immediately" by the two Americans.

"They did not have the possibility to use weapons and react," Gargano said, adding that the officers were attacked as soon as they identified themselves as Carabinieri police officers. That claim contradicts the Americans' own accounts to investigators. They say they didn't know the two officers were police, as they were in plain clothes.

CBS News correspondent Seth Doane reports the suspects were visited in a Rome prison by U.S. Embassy officials on Monday.

Documents released on Monday, in which investigating judge Chiara Gallo explains her decision to allow the continued detention of the pair, provided context of the fatal encounter. The document revealed that the teenagers had been drinking alcohol and that the judge believed they had shown a "total absence of self-control and critical capacity." She said they had "demonstrated an excessive immaturity."

Surveillance video shown by Italian media, though not independently confirmed, purportedly shows the teenagers at the scene in Rome where they allegedly tried to buy about $90 worth of cocaine just before midnight last Friday. They are seen fleeing with a bag they stole after the drug deal went wrong.

An eyewitness said he saw them running away from the scene.

Two plainclothes officers from the Carabinieiri police force were called, including Mario Cerciello Rega, whom Elder has admitted to stabbing. He claims it was self-defense because he believed he was being strangled.

In the court documents released on Monday, however, judge Gallo noted that there were no signs of strangulation found on Elder, and said the multiple stab wounds inflicted on the officer were not indicative of "legitimate defense."

The teens also told interrogators they hadn't realized they were fighting police officers, but Gallo dismissed that as "impossible," saying the officers had identified themselves repeatedly verbally, and shown their badges.

Natale-Hjorth claimed during questioning that he did not know about the stabbing until after he and Elder had returned to their hotel room and had a nap. The teens have offered contradictory accounts as to who hid the murder weapon behind a ceiling panel in their hotel room.

A photo that surfaced of Natale-Hjorth blindfolded in police custody sparked cries of mistreatment earlier this week, especially as it emerged shortly after the police said he had confessed to involvement in the killing.

Italian officials were quick to call the blindfolding of the suspect a mistake by a single officer, who had been moved to a different post amid an investigation into their actions.

On Tuesday, Rome prosecutor Michele Prestipino said stressed that the suspects were questioned by magistrates in a lawful manner, in the presence of lawyers and an interpreter. He said the questioning was recorded.

Prestipino said investigations were still underway to determine why Natale-Hjorth was blindfolded.