About 40 people were involved in the informational session prior to the Giants game at San Francisco's AT&T Park Sunday, the Los Angeles Times reported.
Jonathan Denver, 24, a Dodgers fan, was fatally stabbed Wednesday night during a confrontation outside a bar several blocks from the stadium after he left a game between the Giants and Dodgers.
A suspect, Michael Montgomery, 21, was arrested Thursday and implicated himself in the stabbing, citing self-defense, police said.
San Francisco County District Attorney George Gascon sent the case back to police Friday, releasing Montgomery. Gascon said more witnesses needed to be interviewed to support or rule out justifiable homicide, the newspaper said.
Montgomery was released and had not been charged.
At the ballpark Sunday, Denver's father, Robert Preece, pleaded for witnesses to come forward, noting, "I also understand that the Montgomery family is likely suffering as well," and asked for help "so that both families can have some measure of closure."