Giovanni Ramirez, 31, is associated with the Varrio Nuevo Estrada street gang, one of 34 gangs in a 15-square-mile area east of downtown Los Angeles, said Jose Carrillo, the lead detective in the case.
Ramirez was arrested Sunday and ordered held on $1 million bail.
Ramirez was convicted of attempted robbery in 1998, robbery in 1999 and firing a weapon in public in 2005, Carrillo said. He said Ramirez has been cooperating with authorities while in custody, though he declined to elaborate.
Authorities say he was taken into custody shortly after 7 a.m. Sunday after police served warrants at a home and an apartment building in connection with the assault that led to Bryan Stow, a 42-year-old father of two from Santa Cruz, California, being put into a coma.
Stow was attacked in the stadium parking lot following the first game of the Dodgers' and Giants' seasons on March 31. His mother, Ann Stow, told HLN's Jane Velez-Mitchell last week that it "was a random act of violence against somebody who was wearing Giants colors."
Police withheld Ramirez's identity until his booking Sunday evening on an assault with a deadly weapon charge. In addition to Ramirez's arrest in East Hollywood, police seized evidence and detained several others -- all of whom Los Angeles police said they expected to release after they were questioned.
"This investigation is in its very early stages," Police Chief Charlie Beck said Sunday afternoon outside the stadium. "There are at least two other suspects who we are actively looking for."
Stow's assault has galvanized law enforcement and other authorities in Los Angeles. In particular, security has clamped down at the park in the Chavez Ravine section of Los Angeles.
More than 300 billboards -- which advertise "Wanted" and "Attempted Murder at Dodger Stadium" -- have sprung up around the Southern California city, featuring composite sketches of the suspects. Meanwhile, a $250,000 reward -- including money from the Dodgers, ace Giants pitcher Tim Lincecum and others -- was offered for information leading to the beating suspects' arrests.
Beck assigned 20 detectives to work full-time on the case, saying that as of Sunday afternoon, they'd cumulatively worked more than 6,000 hours -- about 1,000 of those hours on overtime.
He added that police had pursued more than 630 leads from the public and law enforcement. That included a tip from a parole officer that Beck said led to Sunday morning's arrest.
"No matter how small or insignificant it may have seemed at the time, each fact was a critical piece," Los Angeles Mayor Antonio Villaraigosa said of the tips. "And hard work, around the clock, brought us to this (moment) today."
Like Beck, Los Angeles City Council member Ed Reyes urged the two remaining suspects to turn themselves in.
"We're not going to stop," Reyes said. "Let's end this."
Dodgers spokesman Howard Sunkin, reading a statement from owner Frank McCourt, applauded the Los Angeles police force, pledged the team's full commitment to the investigation and promised to make Dodgers Stadium "the safest sports venue in the United States."
Giants President Laurence Baer told CNN affiliate KGO that the arrest was "comforting" for the team and its fans, adding that his best hope is that the incident might spur more civility at sporting events.
"It's been sort of a cloud over the organization," Baer said, adding that he thought that Giants players would probably visit the ailing Stow. "That there's an arrest (and) they can bring someone to justice is ... meaningful."
Stow, a paramedic by training, had gone to the game with friends in celebration of the Giants' World Series victory last season, a relative said.
After the game, two men came up to him in the parking lot and -- unprovoked -- began kicking and punching him while yelling profanities about the Giants, police said.
Ann Stow said her son was first hit from behind, at which point he fell and his head hit the concrete.
"It was just a brutal attack," she said. "Whatever that guy hit my son with, Bryan was unconscious before he hit the ground, so he had no way to protect his head."
The attackers fled in a light-colored sedan driven by a woman with a young boy -- believed to be about 10 years old -- inside, police said.
Stow was taken out of a medically induced coma over a week ago, and has since shown signs of some cognitive function, Los Angeles neurosurgeon Dr. Gabriel Zada said. Stow also has "some movement" in his arms and legs, the doctor said.
He was transferred last week from Los Angeles County-University of Southern California Medical Center to San Francisco General and Trauma Center, bringing him closer to his home, Zada said.
Stow has been able to open his eyes in recent days -- a positive sign, said his mother, even though he still can't focus and is not looking around.
His children know about their father's condition, but still haven't seen him in the hospital, Stow's sister, Bonnie Stow, told HLN. The whole family, she said, is pulling for his recovery and hoping that any brain damage is minimal.
"I don't think it's a matter of him surviving," Bonnie Stow said. "It's just a matter of what he'll be, if and when he wakes up."
This is an interesting notice because it produces experience for the police
