No criminal charges will be brought against five California officers in a fatal Taser encounter with an unarmed man in Millbrae last year, a district attorney announced Friday. Video of the incident was made public Friday afternoon. The decision by San Mateo County District Attorney Steve Wagstaffe comes in the wake of public outcry over the death of Chinedu Okobi, concern over multiple fatal Taser incidents in San Mateo County and mounting calls for the video's release.

Okobi, 36, was unarmed when he died Oct. 3 after being tasered during the encounter with four San Mateo County Sheriff's deputies and a sheriff's sergeant. One of the deputies discharged the Taser, Wagstaffe said.

Speaking Friday, Wagstaffe called the case a "horrible tragedy" and said he wasn't aiming to blame Okobi, a father and graduate of Moorehouse College. He said his investigation found the officers' actions were lawful under the California penal code.

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Okobi's sister Ebele Okobi told CBS News she is devastated by the district attorney's decision, but not surprised. Okobi's was the third death in the span of 10 months involving Tasers and law enforcement in San Mateo, a Bay Area county. Wagstaffe also declined to charge officers involved in the two other Taser deaths.

Chinedu Valentine Okobi CBS San Francisco

Ebele Okobi, who is the director of public policy for Africa at Facebook, said the district attorney's decision means "in San Mateo county, police are allowed to use an unlawful level of force and kill citizens with absolute impunity."

Warning: This video is graphic in nature and contains profanity.

The video released Friday -- a compilation of about 30 minutes of dashcam, cell and surveillance video -- shows a deputy driving in a patrol car and approaching Okobi, who is walking near a busy road. Wagstaffe said the deputy first approached Okobi because Okobi had crossed the road against the light and outside of a crosswalk. Wagstaffe said Okobi didn't comply with the officer's request to talk on a sidewalk and continued to walk in traffic, and the deputy called for backup.

Other deputies responded, and the first deputy warned Okobi he would be Tased. He deployed the Taser when Okobi "continued to ignore instructions" and moved toward the deputy, according to a letter from Wagstaffe to the San Mateo County Sheriff's Office saying the officers would not be charged. In the video, Okobi is seen falling to the ground, asking "What did I do?" and calling for help.

Wagstaffe's letter says the deputy activated the Taser several more times because Okobi was resisting and was "agitated, speaking incoherently, excited." Okobi is then seen running across the street.

Chinedu Okobi with his daughter Okobi family

The letter says the deputy thought the Taser was ineffective and wasn't sure how the officers could detain Okobi, who weighed over 300 pounds, "given his size and strength." The deputy attempted to use his collapsible baton because Okobi's "level of resistance was escalating," the letter says. Okobi is seen swinging at the officer, which the letter says resulted in a seven-centimeter laceration on the officer's face.

Several deputies tackled Okobi and attempted to handcuff him as he struggled, the letter said. They also used pepper spray, but it apparently struck an officer. Deputies handcuffed Okobi and put him in a sitting position when medical personnel responded, according to the letter. As paramedics attempted to move him into an ambulance, they could no longer detect a pulse, and saw Okobi had gone into cardiac arrest, the letter said. Medical personnel weren't able to revive him.

A coroner ruled the cause of death as "cardiac arrest following physical exertion, physical restraint, and recent electro-muscular disruption," and listed cardiomyopathy -- a heart condition -- as a contributing factor. The death was ruled a homicide, Wagstaffe said.

Jeffrey Martin, the use-of-force expert retained by Wagstaffe, found the deputies had probable cause to arrest Okobi because he violated the law when he crossed the street against the signal and refused repeated requests to stop and talk to officers. He also found the officers' use of force as they attempted to detain him to be reasonable.

But the ACLU of northern California released a statement Friday saying that the deadly encounter had "all the earmarks of racial profiling."

"If crossing the street made Okobi the object of police attention and attempted detention – one has to ask if Okobi was white, would the reaction have been the same?" the group said in a statement.

Eugene O'Donnell, a John Jay College professor and policing expert, said the video indicates Okobi was resisting throughout the encounter and did pose a possible risk for deputies. But he cautioned that police enforcement should be a "last resort" for community issues like traffic and pedestrian control. He said it's unclear whether Okobi was posing enough of a danger to himself or others to warrant the initial stop, and warned that police stops for seemingly trivial issues can lead to high-stakes and potentially deadly encounters.

In a Facebook post Friday, Ebele Okobi said Wagstaffe's decision "tells us that we are not safe in San Mateo County. That if you are Black, or mentally ill, or in need of help, or simply walking down the street, you can be electrocuted to death by those meant to protect and serve."

An initial San Mateo County Sheriff's police report says Okobi "immediately assaulted" an officer who approached him, and Ebele Okobi, along with community activists, have accused the sheriff's office and Wagstaffe of releasing misinformation. Ebele Okobi said the video shows her brother was calm and walking on a sidewalk when approached by deputies, not "running in and out of traffic" as the initial statement said.

Activists have also said Wagstaffe has delayed releasing the video. Wagstaffe initially said he planned to release the video in December, but then said he had hired a use-of-force expert and was awaiting his report.

Protesters gather at the San Mateo County District Attorney's Office in January 2019. Charles Moehle, ProBono Photo

Family members and activists have called for a temporary halt on the use of Tasers in San Mateo. The county board of supervisors last month held a public study session to learn more about the devices and local policies governing their use.

Ebele Okobi told CBS News Friday she was shocked that in Wagstaffe's view, "nothing about how the Taser was used was incorrect."

"Nothing about that should give anyone in San Mateo any comfort," Okobi said.

Community activists planned to gather Friday to call for an investigation into Okobi's death by the California Attorney General Xavier Becerra, and an establishment of a permanent civilian oversight committee to review the actions of the San Mateo Sheriff's Office.