Police were called to a fight in a Worthing park in which a man was attacked after allegedly sexually assaulting a teenager.
Officers were responding to reports of a fight in Homefield Park, at 1.30pm on Monday.
Police said a man had been assaulted after he had allegedly sexually assaulted a teenage girl.
A suspect was arrested nearby and taken to custody, confirmed police.
The 32-year-old man, who was detained on suspicion of sexual assault by touching and possession of cannabis, was later released under investigation, said police.
A spokesman said: “Anyone who witnessed either incident is asked to contact police online or ring 101 quoting serial 699 of 03/09.”