(CNN) -- Ex-New England Patriots tight end Aaron Hernandez has been charged with two counts of first-degree murder in the July 2012 killings of two men in Boston, authorities said Thursday.
Hernandez, 24, could be arraigned as early as next week. He is currently in jail awaiting trial in a separate case: the 2013 slaying of Odin Lloyd, who was dating a sister of Hernandez's fiancee.
Suffolk County District Attorney Daniel Conley said at a news conference Thursday that a grand jury returned the indictments in the shooting deaths of Daniel de Abreu and Safiro Furtado.
"Mr. de Abreu and Mr. Furtado were ambushed and executed as they drove home along Shawmut Avenue in Boston's South End in the early morning hours of July 16, 2012," Conley said.
In addition to the two counts of first-degree murder, Hernandez also has been charged with three counts of armed assault with intent to murder and one count of assault and battery by means of a dangerous weapon, the district attorney added.
The latter four counts reflect shots fired at three people, one of whom was wounded, inside the car that de Abreu and Furtado were in, Conley said.
Conley said that Hernandez was driving an SUV that pulled up alongside de Abreu and Furtado's car near the nightclub and that the former football star fired a .38-caliber revolver at them.
Hernandez has also been charged with unlawfully carrying the gun he allegedly used in the attack, Conley said. The gun has been recovered by authorities.
CNN's calls to Hernandez's attorney were not immediately returned.
He 'may have been the shooter'
Confirmation that Hernandez was suspected in the Boston slayings came when documents were unsealed in court in January.
In those records, it is suggested that Hernandez was the trigger man in de Abreu and Furtado's killings.
"There is ... probable cause to believe that Aaron Hernandez was operating the suspect vehicle used in the shooting homicides ... and may have been the shooter," reads a June 2013 warrant that was part of the unsealed batch of records.
The warrant was used to search a Toyota 4Runner linked to Hernandez that, according to court documents, witnesses saw at the scene of the crime. The warrant gave permission to search for gun residue on the SUV, which was recovered at the home of Hernandez's uncle in Bristol, Connecticut.
In search warrant affidavits, investigators have said Hernandez and another man, later identified as Alexander Bradley, followed de Abreu and Furtado into the club.
The former star football player and Bradley are seen on security cameras together inside Cure Lounge and driving an SUV that had been following de Abreu and Furtado when they left the club, according to court papers. Witnesses said that the SUV sped away after multiple shots were fired at the car.
In February, the de Abreu and Furtado families filed wrongful death lawsuits against Hernandez, with each family seeking $6 million.
They said Thursday they were thankful that the justice system was moving forward with criminal charges.
"They have wanted some kind of accountability and they feel as if that is starting to happen," attorney William Kennedy told reporters while flanked by the fathers of the two men.
July 2012 shooting
At Thursday's news conference, Conley described the night that de Abreu and Furtado were killed.
About 12:30 a.m. on July 16, 2012, de Abreu and Furtado arrived at the Cure Lounge in Boston's theater district.
By coincidence, Hernandez and another person entered the club at the same time, Conley said, adding that the investigation has not uncovered evidence that the two sets of men knew each other. Instead, he said, it seems that their "chance encounter" inside the club "triggered a series of events that culminated in these murders."
The victims left the club about 2 a.m. and drove away, unaware, the district attorney said, that Hernandez was driving behind them.
When the victims' car stopped at a red light, Hernandez's SUV pulled up beside it.
"Aaron Hernandez then fired a .38-caliber revolver multiple times from the driver's side of his vehicle into the passenger's side of the victims' vehicle," Conley said.
De Abreu, the driver, was shot several times and fatally hit in the chest, and Furtado, who was in the front passenger seat, was struck multiple times and gravely wounded with a shot to the head, the district attorney said.
Two backseat passengers escaped injury and ran from the car. A third man remained in the car and suffered a wound to his arm, Conley said.
June 2013 shooting
Law enforcement has focused on Hernandez since he was arrested in June. He was charged with first-degree murder and weapons charges in connection with the shooting death of Lloyd, a 27-year-old semipro football player, in North Attleboro, Massachusetts, about a mile from Hernandez's home.
On June 17, a jogger found Lloyd's body riddled with gunshot wounds at an industrial park.
Prosecutors have said that on that day, Lloyd was seen was seen around 2:30 a.m. with Hernandez and Hernandez's friends, Carlos Ortiz and Ernest Wallace, in a rented silver Nissan Altima.
On June 18 and 22, police searched Hernandez's home. Days later, the football player was arrested and charged with first-degree murder in Lloyd's death. Hernandez also was hit with five weapons-related charges.
In court on June 26, First Assistant District Attorney Bill McCauley said that Hernandez "drove the victim to the remote spot, and then he orchestrated his execution."
"He orchestrated the crime from the beginning," McCauley said. "He took steps to conceal and destroy evidence, and he took steps to prevent the police from speaking to ... an important witness."
Hernandez pleaded not guilty, and a judge ordered him held without bail.
The NFL's Patriots then dropped the tight end from the team roster.
On Thursday, Lloyd's sister, Olivia Thibou, said the new indictment of Hernandez shocked her.
"It's pretty scary to hear that someone was on the street, in the public eye, and is such an icon, and now we learn that this is (allegedly) happening behind the scenes," she said.
After the July 2012 double homicide, Hernandez continued to play football. During the next season, he had 51 receptions for 483 yards and five touchdowns. The Patriots finished the regular season with 12 wins and four losses and won the AFC East Division. They lost to the Baltimore Ravens in the AFC championship game.
At the June 26 hearing, defense attorney Michael Fee said that the evidence against his client was circumstantial and that bail should be granted so that Hernandez could return home to spend time with his fiancée, Shayanna Jenkins, and his child, then 8 months old.
"It is a circumstantial case. It is not a strong case," Fee said, arguing that Hernandez had cooperated with law enforcement and was not a flight risk.
While investigators worked, and the former football star stayed in jail, the Lloyd case took several twists and turns.
Last month, Hernandez's associates, Ortiz and Wallace, were indicted on murder charges in connection with Lloyd's killing.
"Ernest Wallace did not shoot or kill anybody," Wallace's attorney, David Meier of Boston, told CNN on April 11.
Wallace pleaded not guilty Thursday to the murder charge in court in Fall River.
Among Hernandez's jail visitors have been his fiancée and cousin, Tanya Cummings Singleton, both of whom face charges in connection with the Lloyd homicide, the court papers revealed in February.
Prosecutors on Thursday announced that Singleton was charged with criminal contempt of court in connection with the de Abreu and Furtado slayings.
The grand jury has also returned an additional indictment charging Singleton with criminal contempt of court, Conley said.
Last October, Jenkins pleaded not guilty to perjury charges after prosecutors alleged that she lied to a grand jury and disposed of evidence.
CNN's Susan Candiotti and Laura Dolan contributed to this report.