Denver was stabbed just blocks from AT&T Park, where he had been watching a Giants-Dodgers game with his family and friends to celebrate his father's birthday.
Toward the end of the night game, 24-year-old Denver, his brother and their brother-in-law headed to a bar. They had just left the bar when they encountered 21-year-old Montgomery and a group of companions around 11:30 p.m.
Accounts differ on who started the fight, but it began with the two groups swapping insults about the Giants and the Dodgers, longtime rivals. Denver and his brother were wearing Dodgers gear; someone in Montgomery's group was wearing a Giants cap.
"While it is not clear how the fatal encounter started, what the evidence shows was a physical confrontation between the victim, the victim's brother and Mr. Montgomery," Gascon said in the statement. "The totality of the evidence revealed that during the physical confrontation, Mr. Denver punched Mr. Montgomery."
Calls made to Gascon for additional information were referred to spokesman Alex Bastian, who in turn referred to Gascon's statement. Bastian did not respond to additional questions sent to him by email, per his request.
According to the district attorney's statement, Denver's older brother, Preece, struck Montgomery in the head with a collapsible aluminum chair at around the same time that Denver punched Montgomery. Under those circumstances, Montgomery inflicted a single, fatal stab wound, Gascon said.
"Independent witnesses as well as the victim's own brother corroborate these facts," he said. "With multiple sources indicating how the event transpired, it makes it impossible for us to meet our burden and prove beyond a reasonable doubt that Mr. Montgomery was not acting in self-defense."
But Denver's brother this week contested key details in Gascon's report on the incident. He said Montgomery's larger group of seven or eight people provoked the fight, pushing Preece, Denver and their brother-in-law, Joey House, following what Preece thought was just a good-natured ribbing about baseball.
"We took it out of fun," he said. "The whole reason we were in San Francisco was to have a good time."
The shoving escalated and someone in Montgomery's group knocked House unconscious, Preece said.
Preece acknowledged that he swung an aluminum chair "in self-defense." He said he knows he hit someone with the chair, but he's not sure whom.
Preece said he and his brother had gotten House off the ground and were trying to leave the fight when Montgomery and some others followed them and the brawl began again. That's when his brother was stabbed, he said.
Michael Montgomery and his father, Martin Montgomery, could not be reached for comment, though Martin Montgomery told the San Francisco Chronicle last fall that his son acted in self-defense.
Jonathan Denver's family said the manner of his death was particularly devastating because it ran contrary to the way Denver lived his life.
"He was the boy with the smile; the man everyone wanted to be around" Diana Denver said, describing her son as mellow and level-headed. "When you were feeling your lowest, he'd walk in with that goofy smile."
Denver grew up in Fort Bragg and for the last couple years of his life worked at North Coast Plumbing, Heating & Sheet Metal. More than 300 people attended his memorial service, his family said.