LONDON (Reuters) - A man had been arrested on suspicion of supplying a firearm as part of the investigation into the fatal shooting of a British police officer, London police said on Sunday. Matt Ratana, a 54-year-old custody sergeant who was originally from New Zealand, was shot dead inside a police station on Friday by a man who was handcuffed. The man is then believed to have turned the gun on himself. “A man has been arrested in the early hours of Sunday 27 September in Norwich, Norfolk, on suspicion of supplying a firearm,” London’s Metropolitan police said in a statement. A man who is the suspect remains in hospital. “He is in a critical condition and consequently we are not able to speak to him,” the police said.