The father of an American teenager arrested on suspicion of killing an Italian police officer said his son was unaware his friend was carrying a knife.
Gabriel Christian Natale-Hjorth, 18 and Finnegan Lee Elder, 19, were charged with aggravated homicide following the death of policeman Mario Cerciello Rega, who was stabbed trying to make an arrest.
In an order for them to be kept in jail, seen by Reuters, a judge said Elder had admitted he had stabbed a man.
"Gabriel didn't know his friend was armed. He only found out what happened, that the officer had died, after his arrest," Fabrizio Natale told the Corriere della Sera daily after visiting his son in Rome's Regina Coeli jail.
"The meeting was emotional but very hard for both of us. He's in a bad state," added Natale.
But police say it is "impossible" that Natale-Hjorth did not know his friend had the knife.
Natale-Hjorth allegedly held Cerciello's partner Andrea Varriale down while Cerciello was attacked.
The two Californian teens had been drinking when the attack took place, and Elder was also on prescription drugs, police said.
Cerciello and Varriale had been asked to intercept the pair after an intermediary on a drug deal reported them to the police for stealing his bag after they found out they were sold aspirin instead of cocaine.