Facebook executive demands answers after her unarmed brother died when police Tasered him four times in busy California street

Chinedu Valentine Okobi with his 12-year-old daughter. He died when he was tackled to the ground by police and Tasered at least four times

A Facebook executive is demanding answers after her brother died while being repeatedly Tasered by police in San Francisco earlier this month.

Chinedu Valentine Okobi, who had been darting in and out of traffic on a busy downtown suffered a heart attack after being tackled to the ground by county sheriff's deputies and Tasered at least four times.

He was unarmed when San Mateo County sheriff's deputies took him to the ground to subdue him on October 3.

Authorities say the 36-year-old black man may have been suffering from a 'mental break' at the time he encountered police. 

Steve Wagstaffe, the San Mateo district attorney investigating his death, told reporters the 6ft 3in tall, 330 pounds, man was subdued due to his size as he 'immediately assaulted' a deputy.

At least five deputies were involved in the detention and one was assaulted as soon as officers approached, with two deputies firing their stun guns a total of four times, police say.

A recording of the incident is said to show part of the moment he was tackled, with Chinedu shouting 'what have I done?’, as he broke free before being grabbed again.

John Burris, a civil rights attorney representing the Okobi family, told the San Francisco Chronicle: 'All I know is a young man's dead and he was in custody of the police. He was unarmed, not engaged in any serious crime.' 

The public statement from the sheriff's department suggested deputies intervened to stop Chinedu getting injured by passing vehicles, his sister Ebele Okobi said.

Facebook's director of public policy for Africa, who moved to London four years ago due to the racial tensions in America, is demanding an investigation into the police tactics used to subdue her brother in the fatal incident.

She says the family have been given little details about the case and do not even know when or where Chinedu, who has a 12-year-old daughter, died.

The 44-year-old told the Guardian: 'Chasing him down and tasing him, there's a protocol for dealing with people in crisis, and that's not it.

'All we know is what we're piecing together from news reports and from video that people are sending us.' 

Ebele has accompanied Facebook boss, Mark Zuckerberg,  to Africa and adds there has been an outpouring of support from top executives at the technology giant, including chief operating officer Sheryl Sandberg.

Her brother's death Millbrae, California, happened just miles from her company's headquarters in Silicon Valley. 

She told USA TODAY: 'There's a part of me that's angry that this is the reality for everybody black I know and that people can live completely oblivious to that reality.

'I didn't think this could happen to someone I know.'

'I think this has helped people who aren't African American and who aren't in the African American community recognize that this is something that every black person faces.

'I definitely think within Facebook, for a lot of my friends and my colleagues, there has been this realization and this recognition that this is a significant national problem.'    

A memorial service for Chinedu, who was the youngest of five siblings, was held on Monday.