Footage has emerged on the internet of the shirtless man apparently being bitten in the neck in the incident in Weston-super-Mare.
Assistant Chief Constable Louisa Rolfe of Avon and Somerset Police said
"The incident has been referred to our professional standards department for thorough investigation as we are keen to understand what happened."
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Sunday has the best of the weather this weekend, looking fine and sunny with high temperatures. Some showers around on Saturday.
Police have this afternoon confirmed they have arrested two people in connection with a shooting in Somerset last night
More than 2,000 young people are gathering on Dartmoor today ready to take part in the Ten Tors challenge.