(CNN) -- An accidental dance floor bump and a spilled drink agitated then-New England Patriots player Aaron Hernandez before he allegedly shot and killed two men in Boston, an assistant district attorney said Wednesday during Hernandez's arraignment.
The arraignment, in which Hernandez pleaded not guilty to two counts of first-degree murder and other charges, had prosecutors revealing the most details to date about a possible motive in the July 2012 killings of Daniel de Abreu and Safiro Furtado.
Hernandez, 24, has been jailed since his arrest last year in connection with the June 2013 slaying of Odin Lloyd in southern Massachusetts. Authorities began investigating him in the 2012 slayings after his arrest in the Lloyd case. He wasn't indicted in the double homicide until this month.
Hernandez attorney Charles Rankin objected to the court letting Suffolk County Assistant District Attorney Patrick Haggan give "a speech" about the prosecution's case, arguing that the prosecutor was trying to poison the jury pool.
Authorities say Hernandez and a friend -- driving from Connecticut to Boston -- arrived at Boston's Cure Lounge in the early morning of July 16, 2012.
Hernandez didn't know the victims before that night, and had no interaction with them until a dancing de Abreu accidentally bumped into Hernandez -- spilling some of Hernandez's drink -- as the Patriots tight end stood at the edge of a dance floor, said Haggan.
"(Hernandez) became angered and increasingly agitated, particularly after Mr. de Abreu smiled and did not apologize," Haggan said.
No argument was seen, and the eventual victims weren't "even aware that the defendant had become angered or agitated," Haggan said.
Hernandez told a friend at the lounge "that Mr. de Abreu had deliberately bumped him and was, quote, 'trying him,' " Haggan said.
Investigators believe that Hernandez, in prior months, "had become increasingly sensitive and angered by what he believed to be people testing, trying or otherwise disrespecting him when he frequented nightclubs in the area," according to Haggan.
The friend, attempting to calm Hernandez, walked him outside, and they eventually entered a club across the street, the prosecutor said. At the second club, Hernandez pointed out a small group of men and told his friend he believed that the man who bumped into him at the Cure had followed him, Haggan said.
"Witness testimony and video surveillance reveal, however, that the defendant's belief was mistaken, as the victims never left Cure lounge until after 2 a.m.," Haggan said.
Hernandez and his friend left the second club and returned to the SUV in which they'd arrived, Haggan said. They drove around, and at some point they pulled over on a nearby street, Haggan said.
Hernandez retrieved a revolver from the engine block of the SUV, where he had hidden the gun shortly before he and his friend left Connecticut, Haggan said.
The 2012 shootings
Authorities previously said that the victims and three of their friends left the Cure Lounge and drove away, unaware 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," Suffolk County District Attorney Daniel Conley said earlier this month.
De Abreu, the driver, was shot several times and fatally hit in the chest. 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.
Defense attorney: Prosecution trying to poison jury pool
In addition to the two counts of first-degree murder, Hernandez also pleaded not guilty to 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 said.
After the July 2012 incident, 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.
Authorities say they began investigating Hernandez in the 2012 killings after they found the SUV -- at a Connecticut home of Hernandez's relatives -- while investigating him in the 2013 Odin Lloyd case.
Hernandez, already held without bail in the Lloyd case, also was ordered held without a bail opportunity in the 2012 case.
Rankin, the attorney for Hernandez, objected to Haggan's extended remarks.
"There is no reason at all to have a speech by the district attorney's office about what they say the facts are, and the court has just played along with that," Rankin said. "This is not supposed to be a spectacle. This is not supposed to be a sporting contest."
"I object to the court giving the district attorney's office an opportunity to present its one-sided view of the case after a one-sided grand jury proceeding," Rankin said.
The judge noted that Rankin also had an opportunity to speak, and that to prevent the prosecution to speak about the case would violate "custom and procedure that dates back quite a few years."
The next court date was set for June 24.
The 2013 Odin Lloyd killing
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.
Hernandez pleaded not guilty. The NFL's Patriots then dropped the tight end from the team roster.
Last month, Hernandez's associates, Ortiz and Wallace, were indicted on murder charges in connection with Lloyd's killing. Both have pleaded not guilty.
CNN's Susan Candiotti, Laura Dolan, Ashley Fantz and Lorenzo Ferrigno contributed to this report.