The move came just as Grant's family was demanding a fresh look at the case in light of what they called new evidence, and in the wake of national calls for greater police accountability.
Nearly 12 years after her son Oscar Grant was shot and killed by BART police officer Johannes Mehserle at the Fruitvale station, Wanda Johnson wants the case reopened and potentially new charges levied against at least one other officer on the platform.
"Justice delayed is justice denied," said Johnson, as she stood before a giant mural of her smiling son at the Fruitvale BART station. "We will continue to be out here and remind people of how are judicial system is continuing to fail people of color."
RELATED: Witness tells jury Grant never resisted officers
Mehserle was convicted of involuntary manslaughter a year and half after the shooting by a Los Angeles jury and served 11 months in prison.
Grant's family now wants prosecutors to reopen the case and file criminal charges against former BART officer Tony Pirone, who was seen in cell phone video holding Grant down in the seconds before he was shot.
"Oscar's last words were 'I can't breathe,'" said Bobby Johnson. "Anthony Pirone, the BART officer who created the climate of violence pinned Oscar down with his knee on his neck, with his hands on his face."
As the Grant family spoke, Alameda County District Attorney Nancy O'Malley announced that she heard their calls.
"We are reopening our investigation," said O'Malley in a written statement. "I have assigned a team of lawyers to look back into the circumstances that caused the death of Oscar Grant. Will evaluate the evidence and the law, including the applicable law at the time and the statute of limitations and make a determination."
RELATED: Court: LA County owes $8M to family of man killed in similar circumstances to George Floyd
"We have listened closely to the requests of the family of Oscar Grant. The murder of Oscar Grant greatly impacted the county and the state," the statement said.
The original trial took place in Los Angeles due to a change of venue ordered by the court on the motion of the defense, where "unfortunately," the jury "only found Officer Mehserle guilty of involuntary manslaughter," O'Malley said.
"We're not holding our breath," said Bobby Johnson after the announcement, "but we're definitely praying that she sees the truth in this issue."
Pirone was fired by BART police, but was never charged criminally in Grant's death.
Mehserle's attorney Michael Rains told KGO-TV, Eyewitness News' sister station, that he does not believe his client could be charged again under the law, given his conviction 10 years ago.
RELATED: Ban on chokeholds among California criminal justice reforms
Rains also says Pirone was an agitator on the platform prior to the shooting.
"He briefly kneeled on Mr. Grant's shoulder and neck area to hold him down. When he heard Mr. Mehserle announce that he was going to use his taser, officer Pirone got up and there was no obstruction of Mr. Grant's airwaves. There was nothing in the autopsy that suggested his breathing was obstructed," said Rains.
Rains doesn't believe the District Attorney has any new evidence to charge Pirone. Instead he believes this move is to appease the family during the current climate.
"For them to now say 'well yeah we should reopen something' when we looked at as long and hard as we did 11 years ago... it just strikes me that it is playing to the hysteria of the moment and the demands of the family," said Rains.
As to what Pirone could've faced decades ago, Rains replied, "They could've charged him with things such as conduct on becoming unprofessional for the way he carried himself. But in terms of criminal charging I'm not sure what kind of charges could've been made."
Below is the full statement from the Alameda County District Attorney's office:
"We have listened closely to the requests of the family of Oscar Grant. The murder of Oscar Grant greatly impacted the county and the state. My Office conducted the intensive investigation that led to the prosecution of BART Officer Johannes Mehserle for the crime of Murder. The trial occurred in Los Angeles due to a change of venue ordered by the court on the motion of the defense. Unfortunately, the Los Angeles jury only found Officer Mehserle guilty of Involuntary Manslaughter. We are reopening our investigation. I have assigned a team of lawyers to look back into the circumstances that caused the death of Oscar Grant. We will evaluate the evidence and the law, including the applicable law at the time and the statute of limitations and make a determination."