Activists in San Mateo County, California are demanding the public release of videos that show an encounter between deputies and an unarmed black man who died last October after being tasered. Family members of the victim, 36-year-old Chinedu Valentine Okobi, have seen the videos and say they contradict the police account of the incident.

Okobi's was the third death in the span of 10 months involving Tasers and law enforcement in San Mateo, a Bay Area county. Family members and activists are calling for a temporary halt on the use of the devices, which fire probes that deliver a pulsed current to temporarily incapacitate a person. The county board of supervisors has organized a study session, set for Monday, Feb. 11, to learn more about the devices and local policies governing their use.

Chinedu Okobi was unarmed when he died Oct. 3 after being tasered by San Mateo County Sheriff's deputies. A statement at the time from the sheriff's office said a deputy first approached him because he was "running in and out of traffic," and he "immediately assaulted an officer," who called for backup. It says Okobi struggled with responding officers and was taken into custody and transported to the hospital, where he died. The statement, which says the incident "did not involve gunfire" but makes no mention of a Taser, says the officer who was assaulted was treated for injuries.

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But Okobi's sister, Ebele Okobi, said she's seen footage — including dashcam, cellphone and surveillance video — that contradicts that account. Ebele Okobi, who works for Facebook as director of public policy for Africa, says she's devastated by her brother's death — and now also fears it's not being investigated properly.

"The initial death is impossible to get over, but on top of it is the message that your loves one's life doesn't matter — that nothing will happen," she told CBS News.

Chinedu Valentine Okobi CBS San Francisco

Ebele Okobi said the videos show her brother — a father and graduate of Morehouse College — walking on a sidewalk before the incident when a deputy pulled up alongside him in his patrol vehicle and said he needed to question him. In a lengthy Facebook post in November, she said her brother gave an inaudible answer and then crossed the street. She said the deputy then called in a "Code 3," meaning to send back-up for an emergency.

A second deputy arrived and ran out of her squad car, rushing into Chinedu Okobi and ripping off his jacket, Ebele Okobi wrote. As he tried to run, another deputy tasered him.

Ebele Okobi wrote the video never shows her brother assaulting an officer, only holding his hands up and falling as he is tasered, yelling "What did I do?"

Ebele Okobi said her brother tried to run across the street and the deputies chased him, tasered him, pepper sprayed him and jumped on top of him.

Ebele Okobi described the videos as "shocking." She says they show her brother dying and no one attempting to help him. "There is no mercy or compassion for my little brother," Ebele Okobi, who lives in London, wrote. "If they had killed a dog the way they killed my brother, there would be outrage."

A coroner's report and cause of death have not yet been released.

Activists pushed for the release of San Mateo Sheriff's Taser use policy in the wake of the death. The policy, obtained by the ACLU of Northern California through a public records request, allows for Taser use "to overcome active resistance from dangerous, violent, or potentially violent subjects who are lawfully arrested or subject to lawful arrest, or who demonstrate intent to cause immediate harm to individuals other than themselves."

But Ebele Okobi says her brother posed no threat to officers. In the post, she acknowledges her brother suffered from mental illness, but says the videos show that wasn't a factor in his death.

"I knew that my brother didn't 'attack' or 'assault' deputies, but because of his mental illness, I believed it was possible that he might have been in crisis and acting erratically," Ebele Okobi wrote. "None of that would have justified him being killed, but there isn't even a reason, at all, that my brother was stopped. My brother's medical history has nothing at all to do with why he was stopped and killed."

The Okobi family's lawyer, John Burris, questioned the reason for the police stop.

"My point of view is this is a man walking while black, by himself, minding his own business, and police just stopped him for no apparent reason other than the fact that he was a black man walking," said Burris, who has seen the videos.

San Mateo County District Attorney Steve Wagstaffe is conducting an investigation. He confirmed to CBS News his office showed the videos to the family. The San Mateo Sheriff's office referred questions to Wagstaffe. A spokeswoman said an internal investigation would be launched following Wagstaffe's probe. In the meantime, the deputies involved are back at work, the spokeswoman said.

Push for video release

Three months after Chinedu Okobi's death, Wagstaffe has yet to release the videos to the public.

In November, Wagstaffe told CBS News he was aiming to release them by mid-December. But in a recent interview, he said he's still investigating whether any of the officers committed crimes. He said he will release the videos, along with all of the materials related to his investigation, when he's ready to make a charging decision, likely by mid-February.

Protesters gather at the office of San Mateo County District Attorney Steve Wagstaffe in January to demand the release of videos in the October death of Chinedu Okobi after he was Tasered by sheriff's deputies Charles Moehle, ProBono Photo

Wagstaffe also says he's contracted an outside "use-of-force" expert to help in the investigation, and he is awaiting that report. "If he concludes that this was an unlawful use of force, that's my guidepost," Wagstaffe said. "It he says that it wasn't, that's a fairly important thing, too."

Wagstaffe has said he never claimed Chinedu Okobi attacked deputies; that statement was issued from the San Mateo Sheriff's Office. But Ebele Okobi said Wagstaffe validated the statement by referring to it in media reports and implied her brother needed to be subdued. She called on him to correct the record.

"He's gone ahead and made public statements that have had an impact on public opinion, to leave those out there and not to retract them and to not give the public the opportunity to see what was true, then the victim gets tried in the court of public opinion," she told CBS News.

A group of activists who gathered last month at Wagstaffe's office for a sit-in called for the immediate release of the videos.

"We have steadfastly requested Steve Wagstaffe to release the videos so we the public can see them, but he refuses to do so," said Regina Islas, an organizer of the sit-in and a member of the San Mateo County activist group #JusticeforChinedu. "...He simply says he will release them when his investigation is complete. That's not good enough."

Islas continued, "The fact that he has refused to do so leaves one to wonder, what don't they want us to see?"

Wagstaffe said his heart goes out to Okobi's family. He said he's taken the unusual step of showing the videos to the family before issuing his charging decision, but said he understands the family may have mistrust in his investigation. He said they will have the opportunity to request the California attorney general review his charging decision if they choose to.

"She has a concern that we will be fair, and I totally respect that," Wagstaffe said. "All I can do is do my job as ethics and integrity require me to do, and tell her, if she doesn't like it, here's the alternative."

Two other Taser-related deaths

The circumstances surrounding Okobi's death are not the only ones that remain in dispute.

Warren Ragudo, 34, died after being stunned with a Taser in January 2018 in Daly City. Ragudo's sister called 911 on Jan. 16, 2018, to report her brother was on drugs, "tripping out," and was being restrained by relatives in their home because he was attempting to jump out a window, according to an April 2 letter Wagstaffe issued to the Daly City Police Department clearing the officers involved of criminal responsibility.

Warren Ragudo Duggan's Serra Mortuary

The department had previously encountered Ragudo, who had a history of drug use and resisting officers, according to Wagstaffe's letter. The three officers who responded tried to physically restrain Ragudo, the letter says, but what happened next is in dispute — Wagstaffe's account says Ragudo was struggling and violently kicking the officers, but the family insists he posed no threat.

An officer delivered a "drive-stun" with his Taser twice to Ragudo's lower back, the letter says. A drive-stun, when the device is applied directly to the person's body rather than via fired probes, is intended to gain compliance through pain and generally doesn't cause neuro-muscular incapacitation, according to the device's manufacturer, Axon.

An autopsy would later determine the Taser stuns were among the factors that contributed to Ragudo's death, listed as "cardiopulmonary arrest due to agitated delirium, physical exertion, prone restraint and stun gun applications while under the influence of methamphetamine toxicity." The manner of death was ruled a homicide. A San Mateo deputy coroner wrote in an autopsy report Ragudo's death, though it may have been unintentional on the part of officers, resulted in part "from volitional actions directed against" him.

Ragudo's family has filed a lawsuit claiming Ragudo was already handcuffed and having trouble breathing with an officer placing weight on his torso for several minutes — before he was stunned.

"Instead of helping him, they killed him," family lawyer Stanley Goff told CBS News.

The Daly City Police department wouldn't comment to CBS News, citing the pending lawsuit. In declining to file charges, Wagstaffe wrote in his letter the officers' conduct was "reasonable and justifiable based on the decedent's violent conduct that evening."

"Tragically, Mr. Ragudo went into cardiac arrest and died," Wagstaffe's letter says. "This unfortunate result was not intended by the officers, nor could they have forseen such a tragic outcome from the use of non-lethal force."

Wagstaffe would later use the same language in a Nov. 1, 2018 letter clearing Redwood City officers in the death of Ramzi Saad, a 55-year-old man who Wagstaffe wrote was acting erratically when he was tasered Aug. 13.

Saad, who had a history of schizophrenia and bipolar disorder, had refused to take his medication and had pushed his mother to the ground outside the home they shared before a neighbor called 911, according to Wagstaffe's account. The letter says the responding officer, who was trained in crisis intervention, first tried to calm Saad and asked him to sit on a curb.

Saad appeared to calm down, but then became agitated and swung at the officer, the letter says. The officer deployed his Taser on Saad, who fell, and the officer stunned him again when he wouldn't put his hands behind his back, according to Wagstaffe's account. Saad then grabbed a piece of fruit from a nearby tree and threw it at the officer, the letter says.

The officer loaded another Taser cartridge and again deployed it, but it wasn't clear whether the probes struck Saad, and Saad rolled to his side and grabbed a brick, according to Wagstaffe's account. The officer tried to stun Saad, but instead shocked himself and dropped the Taser, according to the letter. He picked up the Taser and shocked himself a second time, the letter says.

After a struggle, the letter says the officer was able to physically subdue Saad and handcuff him. The officer would later say Saad was "one of the strongest guys" he had ever encountered, according to Wagstaffe's account.

Three other officers arrived and physically restrained Saad, the letter says. One put pressure on Saad's upper back with his knee but relieved some pressure when Saad appeared to stop fighting, according to Wagstaffe's account. Officers monitored him to make sure he was able to breathe and saw he was breathing, but "some moments later" saw he was unresponsive, the letter says. An autopsy determined Saad died of "cardiac arrest occurring during physical exertion, physical restraint and tasering." A deputy coroner also ruled the death a homicide.

Echoing the language he used in Ragudo's case, Wagstaffe found the officer's conduct to be "reasonable and justifiable based on the decedent's violent conduct that evening."

A message left at a number listed for Saad's mother wasn't returned. Redwood City police didn't respond to requests for comment from CBS News.

Taser safety questions

The three deaths are not the first to raise questions over the safety of the Taser. The device is billed by its manufacturer, Axon, as a "safer, more effective use of force" for law enforcement.

A British police officer holding a Taser during a training session Getty

Axon estimates that the Taser, which is used by more than 18,000 law enforcement agencies in 107 countries, has saved 211,460 people from death or serious injury.

In a 2017 investigation, Reuters found 1,005 incidents in the U.S. in which people died after police stunned them with Tasers.

An Axon spokesman told Reuters those numbers exaggerated the risks posed by Tasers, because most of the deaths involved other types of police force. Of the 712 autopsy reports Reuters was able to obtain, the Taser was cited as a cause or contributing factor to death in 153 cases, usually as one of several factors leading to death. The other autopsy reports largely cited a combination of heart and medical conditions, drug use and various forms of trauma, Reuters reported.

"Looking at the number of individuals who died 'following' encounters with police in which a TASER CEW [conducted energy weapon] was used does not equate to the number of individuals who died 'as a result of' a TASER CEW," an Axon spokeswoman said in a statement to CBS News.

The company cites studies finding there have only been 24 deaths as a result of a Taser strike —18 from fatal head or neck injuries in falls after the strike, and six from fires sparked by the weapon's electrical arc.

An Axon spokeswoman said the company doesn't have specific information about the incidents in San Mateo County and can't comment on the circumstances of Okobi's death because it remains under investigation. However, "Axon works closely with its customers to provide them with the resources necessary to safely and effectively deploy Taser Conducted Energy Weapons (CEWs), including those in San Mateo County. Our mission is to protect life, and we prioritize the safety of our customers and the people they serve above all else, which is why we remain committed to developing technology and training for public safety," an Axon statement said.

Both Wagstaffe and San Mateo County supervisor Dave Pine told CBS News they share the concern about the fatal incidents in their county. But Pine told CBS News because decisions over Taser use lie with each of the 17 law enforcement agencies in the county he doesn't anticipate a county-wide moratorium on their use — as Ebele Okobi and activists have called for — being enacted. Pine said the study session he's convening Monday will bring together representatives from Axon, local law enforcement, the ACLU of Northern California, medical professionals and others in an effort to learn more.

"We want to shine a spotlight on the issue of Taser use in San Mateo County," Pine told CBS News. "We want to be educated about this weapon and understand under what condition the sheriff currently uses it, and promote a dialogue within the public and law enforcement to think hard about when and how these weapons should be used."

Wagstaffe agreed. He said he's spoken to the law enforcement agencies in San Mateo twice about best practices for Taser use and plans on a third presentation. He's also considering offering up suggested policy and training changes to county law enforcement departments.

"What we want it to be is a non-lethal tool to help police not go to the firearm," Wagstaffe said.

Yet on three occasions, local residents have died after being tasered. He said, "If it has that potential, it has to be looked a pretty carefully — is there something different that could be done?"