The family of Chris Kaba will be allowed to watch police video of the incident that led to his killing, the Guardian has learned, as the police watchdog insisted evidence and not public pressure led it to investigate an officer for homicide offences. Kaba, 24, who was unarmed, was shot once by an officer from the Metropolitan police on 5 September. The bullet struck him in the head as he sat in the driver’s seat of a car which had come under suspicion in Lambeth, south London. He died just over two hours later. The Independent Office for Police Conduct has placed the officer concerned under investigation for murder or manslaughter and the Met has suspended him from duty. The IOPC denied it buckled under pressure from Kaba’s family or the public and insisted a review of the evidence it had gathered led it to believe the officer should be investigated. Initially the police watchdog, which has struggled to win public confidence, had treated the officer as a witness. It said: “Our decision to launch a criminal investigation was based solely on our review of the evidence which indicated a criminal offence may have been committed.” Investigators are still to interview the firearms officer under criminal caution amid concern from some in policing that the public have still been given no explanation as to why he decided to open fire. Kaba’s family have been unhappy with the IOPC’s conduct and have demanded to see video of the incident. Officers at the scene were wearing cameras and a helicopter fitted with a camera was following the car Kaba was in. An IOPC spokesperson said the family would now be able to see the footage and that discussions had begun with their lawyers about “how we can facilitate their viewing”. Kaba was in a dark Audi car whose registration plate triggered a police alert linking it to an earlier alleged firearms incident. He was not the car’s owner, and after a police pursuit the vehicle was stopped using “tactical contact” in which it was shunted or rammed. After it came to a halt police vehicles boxed it in, and Kaba was shot and fatally injured. Met firearms officers have a longstanding fear that their bosses will betray them when the going gets difficult. One police source said the Kaba case has reignited that concern: “They feel like he has been thrown under a bus by the Met, who are pandering to public perception and have left the officer out to dry.” Most sources do not expect a mass refusal by officers to carry weapons. Doing so would mean a return to regular frontline policing and responding to emergency calls, but the Met is struggling to to recruit and retain enough armed officers. The Met assistant commissioner, Amanda Pearson, said in a statement: “We don’t underestimate the significant impact on the suspended officer and colleagues, and that is why senior colleagues are working closely with them to ensure they are fully supported. “Firearms officers know that on the rare occasions when they discharge their weapons they will face intense scrutiny.”