The cousin of the innocent Brazilian man killed by anti-terror police at Stockwell Underground station hinted today that his family would sue the Metropolitan Police.

Jean Charles de Menezes, a 27-year-old electrician, was shot in the head at close range on Friday, the day after the failed suicide bombings in London. His cousin, Alex Pereira, told BBC Breakfast this morning that the police "have to pay" for the mistake.

Asked if the family was taking legal action, he said: "They have to pay for that in many ways, because if they do not, they are going to kill many people, they are going to kill thousands of people. They just kill the first person they see, that’s what they did."

The 28-year-old added: "They killed my cousin, they could kill anyone."

The Met could face a claim for compensation and damages from the dead man’s family of hundreds of thousands of pounds. Stephen Waldorf was awarded £120,000 after he was shot and beaten in 1983 when officers mistook him for a dangerous armed robber

Within hours of the shooting of Senhor Menezes, the three police marksmen involved handed in their guns and moved to non-operational duties. The highly trained officers will be confined to office duties or unarmed work for the duration of the investigation.

The rules for investigating a shooting by police are rigid. The officers must not handle guns until the conclusion of the investigation by the Independent Police Complaints Commmission (IPCC) on whether the officer who fired the shots and his colleagues acted correctly.

If the officers are judged to have done so, they will return to active duties. If not, they face a disciplinary hearing or suspension and criminal prosecutions on charges of murder, manslaughter or failing to carry out their duties properly.

The results will go to an inquest, the Crown Prosecution Service and Paul Stephenson, the Deputy Commissioner in overall charge of discipline within the Metropolitan Police.

It may be months before the results of the investigation are known. A 32-page guide on the handling of such inquiries sets out a lengthy process. The first steps are being directed by a detective of at least chief superintendent rank from Scotland Yard’s Directorate of Professional Standards, overseen by Deputy Assistant Commissioner Stephen Roberts or Commander Phil Hagon, his deputy.

Today a team of the IPCC’s own investigators, which include former police officers and security service officials, will take over the case under the direction of Nick Hardwick, the commission’s chairman. Independent experts will be used.

On Friday the officers involved in the shooting, from Scotland Yard’s SO19 firearms branch, were debriefed about the operation. Drugs and alcohol tests were taken — officers must not drink alcohol for at least 12 hours before going operational — and the three were offered counselling. The Police Federation, which represents junior ranks, was also on hand and legal advice will be offered.

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