A post-mortem examination has revealed that a man who was found seriously injured in Bilborough died from a gunshot wound.
The victim, who has not yet been formally identified, was taken to the Queen's Medical Centre in Nottingham but later died.
A 32-year-old man has been arrested on suspicion of murder.
Inquiries are ongoing to establish what happened.
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Paul Dadge become the unwitting face of the 7/7 rescue effort after a picture of him helping a woman in the aftermath went around the world.
Speaking to ITV News' Mark Austin on the anniversary of the London bombings, ex-PM says nations around the world will need to respond.
London was in a celebratory mood on 7 July 2005, but everything changed when three suicide bombers attacked the capital's transport network.