Mourners gathered at St Matthew’s Church, Bryson Street to pay their respects to the 36-year-old.
Mr McMahon was taken ill during the incident in Great Victoria Street in the city at about 5am last Thursday.
The PNSI said officers had responded to reports of a man behaving violently on the street and that he suffered injuries while being restrained.
The case was transferred to the Police Ombudsman’s office which confirmed CS spray had been used, but it is not yet known if it contributed to Mr McMahon’s death.
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Mr McMahon’s grieving parents have called for a “swift and thorough” investigation into the circumstances of their son’s death.