Reports in our sister title The News Letter suggest that an attempt was made to claim his pension.
The Irish Times reported that the deceased pensioner was "propped up by two men" as his body was carried into the building.
It said the two men "dropped" the body and fled when staff questioned them.
The newspaper said it understood that a concerned staff member "enquired about the wellbeing of the man being propped up" when the group approached the post office counter.
Carlow mayor Ken Murnane said the local community is absolutely shocked by the reports.
“The whole town is in shock that anyone could actually think of doing something like that, it’s unbelievable,” he told the PA news agency.
“It’s just mind-boggling that anyone could happen to do something like that, it beggars belief. It’s like a Hitchcock movie.”
A Garda spokesperson said gardai are investigating all the circumstances surrounding the unexplained death of an elderly male in the Carlow area on Friday morning.
“The services of the Garda Technical Bureau and the Office of the State Pathologist have been requested,” they said.
“A post-mortem will be conducted by the Office of the State Pathologist, the results of which will determine the course of the investigation.
“No further information is available at this time.”
Irish broadcaster RTÉ reported that earlier in the day, a man had called in to the post office on Staplestown Road and asked to collect a pension on behalf of an elderly man.
That request was refused as staff told him the pensioner had to be present in order to release the money.
A short time later, two men arrived back with a man aged in his 60s who "collapsed" in the post office.
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