But in an interview with the San Francisco Chronicle, his father said his son wielded his knife in self-defense only after "the kid that got stabbed" swung a chair, hitting Montgomery in the head.
"My son defended himself," Martin Montgomery, 47, told the Chronicle. "That's all it was. Everybody's making it look like it was a team rivalry, but really it was two kids walking."
Martin Montgomery did not witness the incident but instead was relaying what his son told him Thursday afternoon, the newspaper reported.
Denver was wearing Dodgers apparel when he left the game early with his father, brother, his father's girlfriend and another friend to go to a bar a few blocks from the Giants' AT&T Park.
While on 3rd Street, they encountered a group of people who were going to a club, authorities said. One of the men in the other group may have been wearing a Giants cap, police said, and there was some jawing between the groups over the rivalry.
The encounter became physical. It ended when Denver realized that he had been stabbed. He died a short time later at San Francisco General Hospital.
Montgomery and another man were detained a few blocks away after the incident.
At a news conference Thursday, Police Chief Greg Suhr acknowledged that the rivalry between the two baseball teams was "one of the most storied" but said the fact that "anybody got in a beef over the Giants versus Dodgers and someone lost their life, it's just senseless."
Denver was the son of a security guard who worked for the Dodgers. The team released a statement, saying they were "shocked and saddened" by the deadly incident.