District Attorney George Gascon said in a statement late Friday that not all witnesses have been questioned, and no independent witnesses have been interviewed in the stabbing death of 24-year-old Jonathan Denver near AT&T Park on Wednesday night.
Denver, who was with father and brother, was cheering on the Dodgers at Wednesday's game at AT&T Park to celebrate his father's 49th birthday. Relatives say they went out for a birthday drink after the game, and that's when the night turned violent.
San Francisco police say Denver was fatally stabbed after words were exchanged with a group of Giants fans, who had just left a nightclub.
"There was a back and forth about the Giant-Dodger rivalry, which deteriorated into a physical fight," said San Francisco Police Chief Greg Suhr.
Relatives say Denver died at the scene in his father's arms.
Michael Montgomery, 21, of Lodi, was arrested for the stabbing. Montgomery's father told the Lodi News-Sentinel that his son was acting in self-defense after his group of friends was "jumped" by the group of Dodger fans, and that he stabbed Denver after Denver struck his son in the head with a chair.
San Francisco's district attorney says he does not have enough evidence to charge Montgomery and that his office can't prove the stabbing wasn't self defense.
Denver's grandparents in Covina, Robert Sr. and Anne Marie Preece, said in a statement their son and grandson are not the type to initiate an altercation.
"Jon was always smiling, and that is how is we will forever remember him," the statement read. "It pains us that Jon was taken from us at such an early age. We feel that this incident underlines a symptom of a society whose values seem to have deteriorated over time. There is a loss of respect for human life, of family values, honesty, and of the benefit of differing opinions."
Denver used to live in Alhambra with his father. Neighbors say his father would often give out tickets to the games to the children in the neighborhood.
This incident is reminding many of the Bryan Stow case. Stow, a Northern California paramedic, was severely beaten at the Dodger Stadium parking lot following the March 31, 2011, home opener between the two longtime rivals. Stow, a Giants fan, suffered a traumatic brain injury from the attack by two men dressed in Dodgers gear. The Stow family released a statement after Wednesday's incident, saying they were shocked by the violence, and their thoughts and prayers are with Denver's family.
Police in San Francisco are still investigating the incident. A second suspect was questioned and released by police on Friday. Police are still searching for two more suspects.
The Associated Press contributed to this report.