Alan Hawe was found dead along with his wife Clodagh and their children Liam, 13, Niall, 11, and Ryan, six, in their house in rural Ireland last Monday morning.
Mourners have been asked to make donations to one of the country’s leading suicide charities, Pieta House, with a collection box being opened during the Requiem Mass.
Gardai believe Mr Hawe killed his wife and children in their home at Oakdene, in the townland of Barconey near Ballyjamesduff, Co Cavan, before taking his own life.
The remains of the family reposed in Lakelands Funeral Home in Cavan town for several hours on Friday with hundreds of people offering condolences and leaving messages of support.
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The funeral service takes place late this afternoon at St Mary’s Church, Castlerahan, and the family will be laid to rest in the adjoining cemetery.
A memorial mass has also been arranged for next Tuesday in St Nicholas’ Church, Windgap, Co Kilkenny.
Mr Hawe was originally from the county and was deputy principal at Castlerahan National School, near where the family lived.
His wife grew up in Mount Nugent, Co Cavan, and she taught at Oristown National School in Co Meath.
In the wake of the tragedy, the National Suicide Research Foundation issued a briefing document on murder-suicide in which it said there is a need for sensitive and factual reporting in order to minimise harm and increase awareness.
Anyone affected by the incident or other incidents can contact the Samaritans on 116 123.