Former NFL star Aaron Hernandez has been indicted in the July 2012 killings of two Boston men, allegations that come a year after what had been a cold case investigation into the late-night drive-by shooting was revived — seemingly by chance — as investigators zeroed in on the former New England Patriot’s alleged involvement in another killing.

A grand jury indicted Hernandez on two counts of first-degree murder, three counts of armed assault with intent to murder and an additional count of assault and battery with a dangerous weapon.

Hernandez is behind bars while awaiting trial on a charge of first-degree murder in the shooting of another man — Odin Lloyd, a semipro football player whose body was discovered last June in an industrial park near Hernandez’s mansion.

Now, prosecutors say the former NFL tight end was the shooter in the July 16, 2012, slayings of Daniel Abreu and Safiro Furtado, who were killed in a drive-by shooting after leaving a popular Boston nightclub.

“Mr. Abreu and Mr. Furtado were ambushed and executed as they drove home,” said Daniel Conley, the Suffolk County district attorney. The Boston Globe first reported the indictment Thursday.

“For us, this case was not about Aaron Hernandez. This case was about two victims, who were stalked, ambushed, and senselessly murdered on the streets of the city they called home,” Conley said.

The new charges, combined with scores of court documents showing Hernandez’s potential links to several other shootings in recent years, paint an increasingly violent portrait of a young man once celebrated as one of the nation’s most promising up-and-coming athletes.

While a small but vocal group of NFL and Patriots fans have rallied around Hernandez in the year since he was charged in Lloyd’s killing, prosecutors’ new allegations suggest the troubling possibility that the 24-year-old millionaire may have played an entire NFL season after participating in the slaying of two men.

The following account of what happened that night is drawn from police documents detailing their investigative efforts and outlining the evidence they believe links Hernandez to the crime.

According to court documents, video surveillance on July 16, 2012, shows Hernandez arriving at Cure nightclub in Boston’s Theater District at 12:04 a.m. driving a 2006 Toyota 4Runner with Rhode Island license plates.

Minutes later, video from outside the club shows Hernandez and a light-skinned Hispanic man entering the club. They walk in immediately behind Abreu, Furtado and three other men who were out that night with the victims.

“This was a chance encounter where two young men . . . basically had an encounter that led to their deaths,” said Boston Police Commissioner William Evans.