HARTFORD, Conn. (AP) -- A Florida man pleaded guilty Thursday in connection with the carjacking and kidnapping of a Connecticut couple, in what authorities called a failed ransom plot that may have been linked to a $240 million cryptocurrency heist.

Michael Rivas, 19, of Miami, was one of six men arrested after a series of events in Danbury on Aug. 25. He pleaded guilty to kidnapping and conspiracy charges in federal court in Hartford. Two others are expected to enter similar pleas in the same court on Friday.

The couple were driving in a new Lamborghini SUV when the suspects forced them out of the SUV, assaulted them, put them in a van and bound them, police said. Witnesses immediately alerted police. Four of the men were arrested after abandoning their vehicles including the van and fleeing on foot, while the other two were later taken into custody at a nearby home the group had rented through Airbnb, authorities said. The couple were injured but survived the ordeal.

Rivas, dressed in a tan prison uniform with his legs shackled during the hearing, apologized for his actions. He said it was a "dumb" decision to help one of his co-defendants carry out what he called a "vendetta." He did not elaborate.

His lawyer, Brian Woolf, said Rivas accepted a co-defendant's invitation to take part in the plot with the hope of getting a share of the ransom money, and he regrets that decision.

The plot was hatched because the suspects "believed the victims' son had access to significant amounts of digital currency," and they planned to demand a ransom from the son to be paid in digital currency," according to a federal indictment.

Just a week earlier, at least two thieves had stolen $240 million worth of Bitcoin in an elaborate scam over the internet and by phone, and then went on an indulgent spending spree on cars, mansions, travel, jewelry and nights out at clubs, authorities said.

Publicly, federal prosecutors and agents have not definitively linked the kidnapping to the Bitcoin theft. Officials have declined to comment on possible connections between the two cases including how the six suspects knew the couple's son had a large amount of digital currency.

But federal agents told Danbury police that the FBI was looking into whether the couple's son was involved in the Bitcoin theft, Danbury Detective Sgt. Steven Castrovinci told The Associated Press. Neither Danbury police nor federal authorities have named the couple or their son.

Assistant U.S. Attorney Ross Weingarten declined to comment after Thursday's court hearing.

In mid-September, federal prosecutors announced that the two men, Malone Lam, 20, and Jeandiel Serrano, 21, had been indicted on charges of conspiracy to commit wire fraud and conspiracy to launder monetary instruments in connection with the cryptocurrency theft.

Court documents say unnamed coconspirators were in on the scam with the two men. Their lawyers have not responded to requests for comment.

Prosecutors said in court documents that Lam, Serrano and the unnamed coconspirators posed as technical support staff for Google and a cryptocurrency exchange while contacting the victim of the theft with an offer to help him with a supposed security breach.

The victim, from Washington, D.C., believed them and gave them remote access to his computer on Aug. 18. That resulted in the alleged thieves making off with more than 4,100 Bitcoin, then valued at more than $240 million, prosecutors said. That amount of Bitcoin is now worth nearly $380 million.

According to prosecutors, Serrano, of Los Angeles, admitted during an interview with federal investigators that he used the stolen currency to buy three automobiles, worth more than $1 million in total, as well as a $500,000 watch. He also said he had about $20 million of the victim's currency and agreed to transfer the funds to the FBI, authorities said.

Meanwhile Lam, a citizen of Singapore who had addresses in Los Angeles and Miami, Florida, was spending hundreds of thousands of dollars a night at Los Angeles night clubs and acquiring custom Lamborghinis, Ferraris and Porsches, prosecutors said. He also was renting two Miami mansions, bought a $2 million watch and had a Lamborghini Revuelto worth more than $1 million.

Federal prosecutors said in court documents that at least $100 million of the stolen funds remained missing.

Exactly a week after the crypto theft, the couple from Danbury, a city of more than 80,000 people along the New York border, were forced out of their SUV in their hometown after one of the carjackers' vehicles rear-ended them and two other vehicles surrounded them. The group assaulted the man with a baseball bat and dragged the woman by her hair as they put them in the van, where the couple were bound with duct tape, police said.

"I'm deeply remorseful for my irresponsible behavior," Rivas told U.S. District Judge Sarala Nagala on Thursday. "I should have known better."

"This is not what my parents taught me growing up," he added.

Rivas and the other five men also are facing kidnapping and assault charges in Connecticut state court. The other men are also from Florida.

Sentencing was set for May 13. The prosecution and defense agreed on sentencing guidelines that call for about 11 to 14 years in prison.