Refugee Action Coalition spokesman Ian Rintoul has confirmed the man was facing charges against a local woman following an alleged incident at a motel earlier this year.
Mr Rintoul says the matter was yet to go to court, but the man had intended to vigorously defend the charges.
Australia's immigration department has confirmed the death of a 32-year-old man at a hospital in the township of Lorengau, but says it is a matter for P-N-G authorities.
It's believed he took his own life early this Monday morning.
Greens senator Nick McKim has told Sky news the case shows both sides of parliament are neglecting those in detention.
The death comes as more than 50 refugees left Manus Island and Nauru for a new life in the United States last week.
More are expected to follow in coming months.