Police say a one-year-old boy who is fighting for his life may have been shot with an air gun.
Emergency crews were called to a home in Bishport Avenue, Bristol, at 4.10pm on Friday after receiving reports that a baby received a serious head injury.
The child was taken to Bristol Children's Hospital, where he remains in a critical condition.
A 24-year-old man and 23-year-old woman have since been arrested in connection with the incident - with officers adding that the pair are not related to the child.
Avon and Somerset Constabulary Detective Inspector Jonathan Deane described the incident as "tragic".
He said: "We have a trained liaison officer with the family of the child and they will be kept updated on the progress of our investigation.
"We're carrying out enquiries at the scene to establish what happened but clearly these are very tragic circumstances.
"We're aware this will have an impact on the wider community and would encourage anyone with concerns to contact their local neighbourhood team.
"If you have information which could help our investigation, please call us via 101 and quote reference 521614112."