DANIELS SANTO, the man arrested last week on suspicion of murder, has died.
The Argentine, 45, was taken to hospital in the capital, Buenos Aires, on Wednesday.
Police said his condition was stable and that his family had been informed.
His arrest last week after his trip to Sacramento was the second of its kind in the US.
A US justice department spokesman said last week that he was in a stable condition in a local hospital.US Attorney General Jeff Sessions said last month that he had ordered a criminal investigation into the death.
“As the Department of Justice, we are committed to doing all we can to ensure that justice is served,” he said.
The suspect, who was born in Uruguay but was originally from the southern city of Monterrey, was arrested in Sacramento, California, on the night of November 16, 2014, by police.
His family, who live in Argentina, were not informed of his arrest.
Police are investigating whether Santo had been involved in an organised crime ring and if there were other people involved.
Santos’ lawyer, Rafael Mendez, said on Wednesday that his client had not received any news about his death.
Mr Mendez said his client would be “deeply saddened by the loss” of his son.
“His son Daniel has not died, nor will his son Daniel be forgotten,” he told reporters.
“Daniel was born and raised in California, he was the son of a lawyer, he had many close friends in the city of Sacramento and he was loved by all.”‘
A good, hard-working man’A friend of Santos family, Luis Gomez, told Reuters news agency that he believed Santo was innocent of the murders.
“He is a good, strong man,” Mr Gomez said.
“I have always said he was innocent.”‘
The first time in my life’Santo was born on December 19, 1973 in Montevideo, Uruguay, to an Italian mother and Argentine father.
His mother had recently divorced his father and moved to Buenos Aires with her two sons.
His father worked as a taxi driver and Santo went to college at the prestigious Universidad Autonoma de Chile.
The family moved to Argentina after Santo’s mother left the country for the US in 1995.
He joined the local police force, which he described as “the best in the country”, in 1998.
Mr Gomez said Santo, a former military intelligence officer, had a keen interest in security matters.
“You don’t see much of a problem when he gets into trouble because he’s a very good guy,” he added.
Santo was charged in August this year with first-degree murder in connection with the murders of a pair of prostitutes, and was released on bail.