OAKLAND — A former transit police officer has been charged with murder in the fatal shooting of an unarmed and allegedly restrained black man in a racially charged case that has outraged residents and community leaders and set off violent protests.

Newly released court documents allege that Johannes Mehserle, who was charged Tuesday, shot 22-year-old Oscar Grant while Grant had his hands behind his back and another officer was kneeling on his neck.

Mehserle is a 2000 graduate of New Technology High School in Napa and a 2006 graduate of the Napa Valley College Police Academy.

Alameda County District Attorney Tom Orloff made the rare decision to file a murder charge against a police officer for an on-duty incident.

“At this point, what I feel the evidence indicates, is an unlawful killing done by an intentional act and from the evidence we have there’s nothing that would mitigate that to something lower than a murder,” Orloff said at a news conference. He said he would not speculate on whether the charge would end up being first-degree murder or second-degree murder.

Witnesses said Grant was lying face down on a train platform at a station in Oakland when the 27-year-old white officer shot him in the back. Grant and others had been pulled off a train after reports of fighting, as New Year’s Eve revelers were shuttling home after midnight.

Allegations that Grant’s hands were behind his back and another officer was kneeling on him were contained in an Oakland police officer’s request to issue an arrest warrant. It said it appeared from cell phone video that “Mehserle shot and killed Oscar Grant while Grant was restrained and unarmed.”

The shooting, captured on cell phone cameras and widely viewed on the Internet, has inflamed long-running tensions in Oakland between law enforcement authorities and many African-American residents.

Hundreds of people have taken to the streets calling for the prosecution of Mehserle, with one rally last week spiraling into violence that resulted in more than 100 arrests and damage to dozens of businesses. Hundred more protesters gathered Wednesday outside Oakland City Hall.

Mehserle surrendered without incident Tuesday at a family friend’s house in an upscale neighborhood on the east shore of Lake Tahoe in Douglas County, Nev., law enforcement officials said.

During a brief court appearance in Minden, Nev., on Wednesday, he waived extradition and was returned to California to face charges. His lawyer, Christopher Miller, said his client had been in Nevada for a few days to get away from the pressures of what was happening in the Bay Area, and there was no effort to avoid arrest.

“As you are all aware there were some death threats, significant death threats, made against him and his family,” he said.

Mehserle could be arraigned as early as Thursday, Miller said.

“As this case moves forward through the justice system and all of the circumstances of that chaotic night become clear, I fully expect Mr. Mehserle will be cleared of the charges against him,” Miller said. He called Mehserle “a fine officer with an excellent work history” who had been on the force about two years.

John Burris, the attorney for Grant’s family, said the news of the charge was “terrific.”

“It is consistent with the evidence I have seen. I think the family will be pleased,” Burris said.

Michael Rains, a former police officer who has represented cops as a lawyer since 1979, called such a charge “extremely rare.” Rains said he knows of no similar prosecutions in Northern California in the 45 years he has been either a police officer or a lawyer.

Rains said that convicting a police officer of murder for firing a weapon while on duty could prove difficult. He said there are many laws and Supreme Court cases to “discourage second-guessing and hindsighting of their actions.” Rains also said that juries typically view police officers favorably.

“Police officers usually have a leg up in the jury box going to trial,” Rains said.