Aaron Hernandez was taken into custody at his home in Massachusetts, less than a mile from where a 27-year-old man was found dead.
The National Football League player Aaron Hernandez, who was charged with murder Wednesday, is also being investigated as the possible gunman in a double homicide in Boston in 2012, according to a law enforcement official. A second law enforcement official confirmed that Mr. Hernandez had been connected to the homicides, which occurred after a fight in a Boston nightclub.
The twin killing at a city intersection early one morning last July remains unsolved. The police knew that Mr. Hernandez had been in the nightclub called Cure that night but considered his presence of no significance.
“They knew he was in there,” the official, who spoke on condition of anonymity because the investigation was continuing, said of the club. “But it was thought that he was just a sports star at the bar.”
When Mr. Hernandez was linked last week to the killing of Odin Lloyd, a 27-year-old Boston semiprofessional football player, the Boston police decided to take another look at his possible role in last year’s killings.
Further investigation led the police to tie Mr. Hernandez to that killing, said the official, who declined to discuss any evidence in the case. The official said that Mr. Hernandez was believed to have fired the shots that killed the two men, Daniel Abreu, 29, and Safiro Furtado, 28.
The fight inside the club took place between Mr. Abreu and Mr. Furtado and a group of men that the police have now been told included Mr. Hernandez.
Mr. Abreu and Mr. Furtado left the club with three other men in a BMW sedan. Mr. Abreu, who was driving, came to a stop at a traffic light when an S.U.V. with Rhode Island license plates pulled alongside. The BMW was than sprayed with gunfire, which killed Mr. Abreu and Mr. Furtado. The three other men in the car survived. No suspects were identified, but the Boston police never closed the investigation.
The killings took place about a week before Mr. Hernandez reported to the New England Patriots’ 2012 training camp. The next month, the team gave him a $40 million contract extension. Mr. Hernandez, a tight end, appeared in 10 games last season and had five touchdowns.
On Wednesday, Mr. Hernandez, 23, was charged with murder and five gun-related offenses in Attleboro District Court in Massachusetts in connection with the June 17 murder of Mr. Lloyd, whose body was found in a secluded section of an industrial park that is less than a mile from Mr. Hernandez’s home in North Attleborough, Mass.
Mr. Hernandez pleaded not guilty and was held without bail. On the murder charge, he faces a life sentence without parole.
One official said investigators were exploring a possible connection between the two cases that could explain a possible motive for the Lloyd killing. The person said investigators were examining the possibility that Mr. Lloyd was killed because he had information about Mr. Hernandez’s suspected involvement in the 2012 double homicide, but cautioned that that was somewhat speculative at this point.
The potential connection to another lethal crime was just one of several developments Thursday concerning Mr. Hernandez, who was released by the Patriots after his arrest Wednesday.
In a bail review court hearing, the prosecutor William McCauley revealed that additional search warrants had discovered .45-caliber bullets in a condominium Mr. Hernandez rented and in a car linked to him. While the weapon in the Lloyd case has not been found, prosecutors have said that Mr. Lloyd was killed with a .45-caliber handgun.
Mr. Hernandez’s lawyers were hoping to have bail set with conditions like a G.P.S. monitoring bracelet, a $250,000 cash bond and house arrest. James Sultan, a lawyer for Mr. Hernandez, also called the prosecution’s depiction of Mr. Hernandez’s role in Mr. Lloyd’s murder “their theory.”
He added that he looked forward to testing the quality of the prosecution’s evidence.
Joe Drape contributed reporting.
