(Updates with arrest of suspect)
By Laila Kearney
SAN FRANCISCO, Sept 26 (Reuters) - A 21-year-old California man was arrested on Thursday in the stabbing death of a Los Angeles Dodgers fan just blocks from the San Francisco Giants baseball stadium in a fight between fans of the rival franchises.
Michael Montgomery of Lodi, California, was booked on suspicion of homicide, San Francisco police said. Police gave no information on a second man who was detained earlier on Thursday and it was not immediately clear if he remained in custody.
Jonathan Denver, the son of a Dodgers security guard, was stabbed by a Giants supporter on Wednesday night blocks away from AT&T Park, police said. Denver, 24, of the Northern California town of Fort Bragg, was taken to a hospital where he died of his wounds.
Denver, who was dressed in Dodgers gear, had been with a group of Dodgers fans who left a bar after Wednesday's game. At around the same time, a rival group left a nearby nightclub, and a shouting match ensued, police said.
"It started off with a back-and-forth: 'Go Dodgers!' 'Go Giants!' and it deteriorated from there," said San Francisco Police Chief Greg Suhr.
The death follows a 2011 attack on Giants fan Bryan Stow, who was badly beaten in a Dodger Stadium parking lot in an attacks that raised concerns about stadium security.
Stow, a paramedic and father of two, suffered brain damage. Two men are awaiting trial on charges stemming from that beating.
"The Dodgers are shocked and saddened to learn of the death of Jonathan Denver," the team said on its official Facebook page. "There is no rational explanation for this senseless act which resulted in Jonathan's death. The pain that this has caused his family and friends is unimaginable."
The deadly fight began just over an hour after the Giants' 6-4 win over the Dodgers, police said. It was not immediately clear which group started the fight, and a murder weapon had not been located, Suhr said.
San Francisco police planned to increase uniformed and undercover patrol operations at a game scheduled for Thursday night between the Giants and the Dodgers. Some police officers would be wearing Dodgers attire, Suhr said. (Additional reporting by Dan Whitcomb; Editing by Alex Dobuzinskis, Cynthia Johnston and Philip Barbara)