Police arrested 21-year-old Michael Montgomery on Thursday. They say he got into an argument with the victim, Jonathan Denver, after the Giants-Dodgers game on Wednesday.
Denver was stabbed to death and police say he was wearing Dodgers gear.
Friday night Montgomery was released from jail.
In an interview with the Lodi News-Sentinel Montgomery's parents claim their son was outnumbered and was hit in the head with a chair, so he fought back in self-defense. That appears to be why he was released.
San Francisco District Attorney George Gascon said they do not have enough evidence to prove murder beyond a reasonable doubt. He said in a statement late Friday that not all witnesses have been questioned and no independent witnesses have been interviewed.