Sēmisi Māvaetangi, 60, was taken from the Nuku’alofa Central Police station to hospital on October 29 but passed away soon after.
Local media reports said it appeared Māvaetangi was unwell before he collapsed.
They said the deceased was arrested following a complaint he and another accused allegedly assaulted a man in Fangaloto.
Māvaetangi and his co-accused were wardens supervising the Popua Community Park when they found a Fangaloto man drinking alcohol there.
They took the man to his home before the alleged assault happened after the man did not cooperate, it has been claimed.
The deceased and his co-accused were scheduled to appear in court yesterday.