A 13-year-old boy was struck with a bottle at a park.
Police were called to an incident at the Bowl park, Mayflower Way, Angmering, at around 4pm on December 21.
The 13-year-old boy was taken to hospital and has since been discharged.
Now, officers are appealing for witnesses to the incident.
A spokesman for Sussex Police said: "Officers were called to an incident at the Bowl park, Mayflower Way at around 4pm on 21 December where it was alleged a child had been bottled."
The alleged attacker was between 5ft 8in and 6ft 1in, skinny and was wearing all black.
Witnesses or anyone with any information is asked to contact Sussex Police online or call 101 quoting serial 902 of 21/12."
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