Police investigate the shooting outside Candlestick Park. (Michael Macor / AP)

One of the shooting victims reportedly was wearing a T-shirt with a profanity directed at the Niners and Amy Trask, the team’s chief executive officer and a member of the NFL Security Committee, defended them, saying most are “terrific people and terrific fans.”

“I'm aware of the perception [of Raiders fans], and I don't believe the perception is the reality,” Trask said. “Stereotypes are insidious. It's so simple to stereotype Raiders fans. It's an easy story. If you are hearing frustration coming through in my voice it's because there's frustration in my voice.”

An investigation continues, with police looking for a person of interest, examing evidence and seeking more witnesses.

A 24-year-old man who was shot several times in a parking lot and managed to drive to a security office for help remained in critical condition, according to Sgt. Michael Andraychack of the San Francisco Police Department. Another man, also in his 20s, remained hospitalized with less serious gunshot wounds. About an hour before the shootings, a 26-year-old San Rafael man was beaten until he lost consciousness in a restroom. He remains hospitalized in serious condition.

“Violence will not be tolerated in either of our stadiums,” the mayors of San Francisco and Oakland said in a joint statement. “Fans come to our stadiums to enjoy an afternoon of football, not to be subjected to intimidation or violence.”

There were numerous fights in the stands — as videos show — in spite of an increased security presence. Andraychak said it’s routinely beefed up when teams have a strong rivalry or when their fans have a history of violence.

The violence is the second involving a major-league team this season. On March 30, a San Francisco Giants fan was beaten in a Dodger Stadium parking lot after a game. Bryan Stow, a 42-year-old firefighter, suffered a severe skull fracture when his head struck the ground. He remains hospitalized and, although he is conscious and able to breathe on his own, he cannot speak. His neurosurgeon said in a statement to the San Francisco Chronicle that he can move slightly on command and turn toward people who speak to him.