In an exclusive interview with ABC News that aired Monday on "Good Morning America," Ethan and Leah Elder said they are concerned about their son's mental health behind bars.
"We just want Finn to be able to survive this," Leah Elder said. "He has a noted history of attempted suicide, and we're really worried and really concerned. He was utterly devastated by the verdict, just devastated. It was completely unexpected for him."
When Elder's mother testified in court in Rome last December, she spoke of her son's suicide attempt at the Torpedo Wharf, a pier in San Francisco that sits at the mouth of the Golden Gate, the one-mile-wide strait connecting San Francisco Bay and the Pacific Ocean. Leah Elder told ABC News that the court-appointed psychiatrist also noted other previous suicide attempts in his report on her son.
"He struggles with anxiety and depression, and his current situation is really perilous," she said.
Prosecutors alleged that Finnegan Lee Elder, then 19, and Gabriel Christian Natale-Hjorth, then 18, attacked two members of Italy's storied Carabinieri paramilitary police force on a street corner in Rome in the early morning hours of July 26, 2019, after a botched drug deal. Police said the teenagers, who are former classmates from the San Francisco area, were trying to buy drugs in Italy's capital but were sold a fake substance. They then allegedly robbed a man who had directed them to the drug dealer in the first place, stealing his backpack and demanding he pay them 100 euros and a gram of cocaine to get it back. The man agreed but, unbeknownst to them, he also contacted authorities, according to police.
Carabinieri Vice Brigadier Mario Cerciello Rega, 35, had just returned to duty from his honeymoon when he responded to the call with his partner at around 3 a.m. local time. Both officers were in plainclothes when they confronted the American tourists on a street near an upscale hotel in Rome where they were staying, according to police.
Elder testified that he and Natale-Hjorth were suddenly confronted by two men who they thought were drug dealers.
A scuffle ensued and Elder allegedly stabbed Cerciello Rega 11 times with a combat knife that he brought with him on his trip to Europe, while Natale-Hjorth allegedly punched Cerciello Rega's partner repeatedly, according to prosecutors.
A coroner concluded that Cerciello Rega bled to death. Italy mourned the newlywed policeman as a national hero.
Elder admitted to stabbing Cerciello Rega, but said he did it in self-defense because he feared that he was being strangled during the four-minute encounter.
Speaking to ABC News, Elder's parents described him as "incredibly kind, incredibly sensitive" and "painfully honest."
"He does not see a reason to lie," Leah Elder said of her son. "From the moment Finn was detained, he has not changed his version of that night one iota."
Police said Elder and Natale-Hjorth were captured on surveillance video fleeing the scene with the stolen backpack. The duo were tracked down at their hotel, a block away from the scene and near Rome's Tiber River. Police said they discovered the knife and blood-soaked clothes hidden in the ceiling of the teens' hotel room.
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.
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Natale-Hjorth testified that he hid the knife at Elder's request and that he didn't know his friend had the weapon on him prior to the stabbing.
In the days after the killing, Italian newspapers published a leaked photo of what appears to be Natale-Hjorth blindfolded and handcuffed while in custody, prompting questions about the pair's confessions. It is illegal to blindfold a suspect in Italy.
Elder's parents told ABC News that their son was "illegally interrogated" by police "without a lawyer present."
"We raised Finnegan, as I'm sure many other parents do, to tell the truth and things will be okay," Ethan Elder said. "And part of his utter devastation at this verdict is he has told the truth from the very moment he was being illegally interrogated."
During a press conference in Rome on July 30, 2019, the Carabinieri commander told reporters that Cerciello Rega had "forgotten his gun" that fateful night, but there was still "no time" for the officers to react and the suspects then took off. 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, the commander said.
The murder trial ended last Wednesday. A jury convicted both Elder, now 21, and Natale-Hjorth, now 20, on all five identical charges and handed them life sentences, Italy's stiffest punishment. Under Italian law, an accomplice in an alleged murder can also be charged with murder even if they did not actually kill the victim.
Cerciello Rega's widow, Rosa Maria Esilio, broke down in tears in the courtroom upon hearing the verdict.
Elder's parents told ABC News they were shocked that Natale-Hjorth was also charged with murder and received the same sentence.
"My heart breaks for that entire family," Leah Elder said.
Elder's parents said they feel their son's sentencing was too harsh, given his mental health issues and young age, and that they plan to appeal the ruling.
"He feels like he has been sentenced to something worse than the death penalty," Leah Elder said of her son.
"I understand that a man's life was lost that night, I understand that Finnegan should serve some time," she added. "I would like Finnegan to have some sort of sentence that's proportionate and something that helps at least acknowledge his mental health issues."
The parents said their son's new reality -- his life as a prisoner -- is at times "too painful" to think about.
"This tragedy that happened, it's changed us all," Ethan Elder said. "Watching your son mature in prison is very hard."
ABC News' Clark Bentson, Mya Green, Phoebe Natanson and Ian Pannell contributed to this report.