A university student was found dead at the house he shared with six people some four days after he was last seen, his father said.
Third-year aerospace engineering student Sean Slootweg, 21, was discovered by a house mate at the digs in Swansea on Thursday last week.
His father Paul would not speculate on how long his son, diagnosed with epilepsy at the age of 18, had been dead before he was found.
"I'm trying not to think about it," he said. "It's clearly a distressing thought. We still don't know when or how and, of course, we will never know why. There may be answers at the inquest in a couple of months' time."
Mr Slootweg said it was also not known whether his son had suffered a seizure - an initial post-mortem examination failed to find a medical cause of death.
But he added: "We have been told his death is not suspicious but when a 21-year-old boy dies without any determinable cause, how can they say?"
Sean, of East Hunsbury, Northampton, was last seen on March 2 and there was activity on his computer until the last minutes of that night, said Mr Slootweg.
He said: "The hardest part is that we have the four-day gap when nobody appears to have any contact with him."
Mr Slootweg, 46, did not want to lay any blame for his son's death but said Sean may have been discovered sooner if others had been "more aware".
His funeral will take place on March 26 St Francis and St Therese Roman Catholic Church in Hunsbury.
