By 2006, the gang was responsible for 70 percent of all shootings here, the police said. In this city of nearly 506,000 people, some 60 percent of the 52 murders that year were gang-related, and most of them pointed to Bulldogs.

As they multiplied, so too did their enemies.

In 2003, while visiting her parents in Atwater, Calif., about 70 miles north of here, Lyndsay Hawthorne, a Fresno State sophomore, went running in her Bulldogs T-shirt. She was trailed by a car full of Sureños who shot at her, shouting that her shirt was not welcome in their town. The bullets missed Hawthorne, sending sparks off the pavement around her.

“It was very scary,” said her father, Richard, who was a commander with the Atwater Police Department at the time. “I took that shirt away from her.”

To grow its numbers, the Bulldogs gang recruited around elementary schools and high schools. In the early 1990s, the gang presence was so big among youth that city schools banned Fresno State Bulldogs clothing on school property. The ban was soon extended to Georgetown Hoyas apparel, which also features a bulldog.

“It is unfortunate because we work hard to create a college-going culture in our schools, but we just cannot have students wearing this stuff; it causes too many problems,” said Tim Liles, the principal at Sunnyside High School in Fresno. Schools here eventually had to ban all attire featuring professional and college sports logos.

Unsettled by the sudden rise of thousands of violent gang members wearing their university’s apparel, officials at California State University, Fresno, requested a meeting with law enforcement officials in 2007. They were considering changing the logo and wanted advice.

“There was considerable discussion at that time about whether or not they should change the logo or the mascot away from being a bulldog because of the fact that we had this Bulldog gang in Fresno that had become notorious,” Dyer, the police chief, said. “My advice was absolutely not. Do not touch the logo. How dare these gang members think they can hijack the mascot from our university? If you change it, the gang wins.”