Italian officer allegedly stabbed to death by American teens had 'forgotten his gun' Deputy Brigadier Mario Cerciello Rega was fatally stabbed in Rome on July 26.

The questioning of two American teenagers who confessed to their involvement in the slaying of a newlywed police officer in Rome last week was conducted lawfully, an Italian prosecutor said Tuesday.

"The suspects were identified and interrogated by the magistrates with respect of the law," Rome's acting prosecutor, Michele Prestipino, said at a press conference. "The interrogations were conducted with all the guarantees of the defense, in the presence of the defense lawyers, of interpreters, and after the reading of all the notifications envisioned by law.”

Prestipino said the interrogations were also recorded.

The prosecutor's comments come two days after Italian newspapers published a leaked photo of what appears to be one of the Americans blindfolded and handcuffed while in custody, prompting questions about the pair's confessions. Italian police and prosecutors are carrying out separate investigations of the blindfolding.

U.S. citizens Finnegan Lee Elder, 19, and Gabriel Christian Natale-Hjorth, 18, remain jailed in Rome on suspicion of attempted extortion and aggravated murder in connection with a botched drug deal and the fatal stabbing of Mario Cerciello Rega, a 35-year-old deputy brigadier in Italy's Carabinieri paramilitary police force.

Cerciello Rega and his partner "were attacked immediately" by the two teens on a street corner in Rome in the early morning hours of July 26, according to Gen. Francesco Gargaro, the commander of the Carabinieri in Italy's capital.

"There were no chance to use weapons," Gargaro told reporters at Tuesday's press conference, adding that Cerciello Rega had "forgotten his gun" that night, but there was still "no time" for the policemen to react and the suspects then took off.

Elder and Natale-Hjorth, both residents of Northern California, were allegedly trying to buy drugs before the slaying, but were sold a fake substance, a police spokesman told ABC News.

They then allegedly robbed a man who had directed them to the drug dealer who ripped them off, taking his backpack and demanding he pay them 100 euros and a gram of cocaine to get it back. The man agreed but, unbeknownst to Elder and Natale-Hjorth, he also contacted authorities, according to the police spokesman.

Cerciello Rega, who had just returned to duty from his honeymoon, responded to the call with his partner at around 3 a.m. local time. Both officers were in plainclothes when they confronted the suspects on a street near an upscale hotel in Rome where the teens were staying.

A scuffle ensued and Elder allegedly stabbed Cerciello Rega 11 times, while Natale-Hjorth allegedly punched Cerciello Rega's partner repeatedly, according to police reports made public on Saturday. Elder allegedly used a 7-inch fix-blade combat knife during the four-minute encounter, according to a court document leaked to media outlets and obtained by ABC News.

A coroner concluded that Cerciello Rega bled to death, according to Italian news reports.

Elder and Natale-Hjorth were allegedly captured on surveillance video fleeing the scene with the stolen backpack. The duo were tracked down a block away at their hotel near Rome's Tiber River, police said.

Investigators also discovered a knife believed to be the murder weapon and blood-soaked clothes hidden in the ceiling of the teens' hotel room, police said.

Gargaro, the Carabinieri commander, told reporters Tuesday that Cerciello Rega's partner could not have used his weapon on the suspects as they fled because it's a serious crime and was trying to help the wounded officer.

Elder and Natale-Hjorth were questioned by police for hours and, when "faced with overwhelming evidence, they confessed," according to the Provincial Command of Rome.

Elder claimed he allegedly stabbed Ceriello Rega in self-defense, telling police he "feared for his life," according to the court document obtained by ABC News.

Investigators concluded that "it's clear that the perpetrator of the stabbing" was Elder, according to the court document.

A funeral for Ceriello Rega was held Monday in his hometown of Somma Vesuviana, in the same church where he and his wife were married six weeks earlier.

Italy's prime minister, Giuseppe Conte, called the policeman's death a "deep wound for the State.”

ABC News' Bill Hutchinson and Ian Pannell contributed to this report.