The case of two U.S. teen tourists arrested in the brutal slaying of an Italian police officer took another turn Tuesday with the revelation that the plainclothes officer didn't have his gun the night he was fatally stabbed.

Deputy Brigadier Mario Cerciello Rega, 35, a newlywed, was stabbed 11 times after he and his partner responded to an extortion attempt allegedly made by the teens after a failed drug deal, Carabinieri Gen. Francesco Gargaro said at a news conference.

The teens, vacationing in Italy on their own and staying in a posh hotel, were trying to get money and cocaine in return for stealing a knapsack, Gargaro said.

Finnegan Lee Elder, 19, and Gabriel Christian Natale-Hjorth, 18, former high school classmates from San Francisco, were detained early Friday in the slaying of Cerciello Rega and jailed in Rome.

Keep up to date with this story:The Evening Briefing newsletter brings the news directly to your inbox

The case has triggered outrage in Italy, garnered international scrutiny and drawn some comparisons to another sensational saga involving a young American: Amanda Knox, a U.S. student studying in Perugia who was accused in the 2007 stabbing death of her roommate. Knox was convicted but later acquitted.

Gargaro said Cerciello Rega had forgotten his gun after being called into service on his day off. His partner, Andrea Varriale, did have his gun, Gargaro said, but "there was no time to use it" because the two were immediately attacked after announcing they were police when confronting the teens.

Under Italian law, it is also illegal to fire at a fleeing suspect, Gargaro said.

Judge Chiara Gallo in a ruling Saturday said the teens told interrogators that they weren’t aware that the men were Carabinieri. But Varriale said the two officers announced they were Carabinieri and showed their badges before being assaulted by the two Americans who were wearing hoodies, Gallo said.

Stabbing death:Italian paramilitary police officer killed by US teenagers, authorities say

On Tuesday, Gargaro provided more details on the timeline that led to the slaying.

The teens had allegedly paid for cocaine from a dealer in Rome’s Trastevere neighborhood, investigators say, but the deal fell through as police approached. Investigators said the two took the knapsack of an Italian man who had given them a contact to buy cocaine.

When the man called his cellphone – which was in the snatched knapsack – the teens told him they’d give the bag back in exchange for 100 euros and a gram of cocaine, police say.

Investigators say the man then reported the extortion attempt to police – who dispatched Cerciello Rega and Varriale to find the teens.

Gargano said Tuesday that Elder claimed he brought the knife with him on his trip from the U.S. a few days earlier.

Elder told authorities during his questioning that he stabbed Cerciello Rega because he feared he was being strangled, Gallo said in her Saturday ruling, noting the teen didn’t have any marks on his neck.

The Carabinieri police force, in a statement, said the two confessed after being interrogated and facing "overwhelming evidence."

Shocking photos:American teen arrested in Italian police officer's death 'illegally blindfolded'

On Sunday, Italian newspapers published a photo of Natale-Hjorth with a blindfold over his eyes and in handcuffs before his interrogation. Blindfolding a suspect is "illegal. It's not allowed," Provincial Cmdr. Francesco Gargaro said. The officer who put the blindfold on Natale-Hjorth did so to prevent him from seeing documents related to the investigation, the commander said.

Cerciello Rega's funeral was held Monday in the same church in Somma Vesuviana, where he was married six weeks ago. Italy’s military chaplain, Archbishop Santo Marciano, said Cerciello Rega lived and died a hero and protector. The slain officer was lauded for his charity work with the homeless.

Contributing: Elizabeth Lawrence, the Associated Press