The family of the Brazilian electrician who was mistaken for a terrorist and slain by British police threatened on Monday to take legal action, but a senior officer insisted the new threat posed by suicide bombers made deadly force a necessary option.

Police shot Jean Charles de Menezes, 27, in a subway car after mistaking him for a suspect in the investigation into Thursday's botched bombing attempts on three subway trains and a bus.

• Man shot dead by London police identified as Brazilian

Officers later said he had no connection to the probe and expressed deep regret for his death.

"They have to pay for that in many ways, because if they do not, they are going to kill many people," his cousin Alex Pereira told British Broadcasting Corporation television.

"They killed my cousin; they could kill anyone," the 28-year-old London [Images] resident said.

But Chris Fox, president of the Association of Chief Police Officers, said police had to have the option of using lethal force to stop suspected suicide bombers.

"We have a series of tactics which range from disruption to the very, very final moment when you have to shoot, and the aim is to prevent the criminal or suspect causing harm to other people," Fox told BBC TV.

Menezes was followed by plainclothes officers after he left an apartment bloc that was under surveillance. Wearing a padded jacket, he boarded a bus and travelled to the nearby Stockwell subway station.

According to officials, his clothing and behavior aroused the suspicions of the police, who ordered him to stop.

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