San Francisco ? The involuntary manslaughter conviction of a white former transit officer in the death of an unarmed black man set the stage for a sentencing that could be just as explosive as the trial depending on how the judge interprets the verdict.

Los Angeles Superior Court Judge Robert Perry has a tremendous amount of discretion in handing down punishment Aug. 6 against Johannes Mehserle — anywhere from probation to 14 years.

A sentence on the low end could further inflame tensions among the hundreds of angry people who took to the streets of Oakland Thursday over what they believe should have been a murder conviction.

Those protesters could find some satisfaction in the way Perry decides to apply a finding by the jury that Mehserle used a gun to commit the crime.

Involuntary manslaughter convictions call for two to four years in prison, but Perry could tack on an additional three to 10 years due to the gun enhancement.

“I think he could get substantial time, by that I mean like six years,” said John Barnett, a defense attorney from Orange County who represented one of four Los Angeles police officers acquitted of beating Rodney King in 1992. “There is going to be a lot of pressure to give him state prison.”

In a handwritten letter released Friday, Mehserle suggested a possible prison term wouldn’t be his only punishment for killing 22-year-old Oscar Grant.

He said he will forever “live, breathe, sleep and not sleep” with the memory of Grant dying on the train platform and “knowing that Mr. Grant should not have been shot.”

In a move reminiscent of the Rodney King beating case in Los Angeles, federal authorities said they will investigate the shooting.

Federal officials stepped into the King case after a state court jury acquitted four Los Angeles police officers in 1992 of using excessive force, touching off three days of riots, 53 deaths and more than $1 billion in damage.

The two officers convicted of federal civil rights violations in the King beating were each sentenced to 2 1/2 years in prison. A federal jury acquitted the two other officers.

The verdict against Mehserle enflamed emotions in Oakland, where 30 businesses were damaged and 78 people were arrested for violations that included failure to disperse, vandalism and assaulting a police officer.

Protesters looted an athletic footwear store and ransacked a jewelry shop. The windows of a bank were smashed, fires were set in several trash bins, and a small incendiary device was detonated near a police station but caused no damage.