John Mullan, 49, and children Tomas, 14, and Amelia, six, from Moville, died when their vehicle plunged off the road into Lough Foyle at Quigley’s Point as they returned from an evening out in nearby Derry on Thursday.
Geraldine Mullan, 45, escaped and raised the alarm.
Fr John Farren said: “Her whole family had been wiped out in one go. She was totally distraught.”
The parish priest of Iskaheen said he prayed with Mrs Mullan over her family’s bodies, which had been placed in a tent at the roadside.
He recalled: “She came into the tent and that was the first time she had seen her family.
“It was a stressful and emotional moment for her.
“I gave her time to get her wits about her then we said prayers and I anointed the three bodies.
“She made a sign of the cross on all three of them.”
The vehicle rolled down a slope and remained lying on the shoreline on Friday, on its roof and badly mangled.
Mr Mullan ran a popular garden centre in Moville and his wife is a nurse manager in the cancer unit in Letterkenny General Hospital, Fr Farren added.
The priest said it was wet and windy when he arrived at the scene of the tragedy shortly before midnight.
It was high tide and the waves were white-tipped.
He said: “It was an awful night, the visibility was poor, it was windy and raining, the road was slippery and had recently been resurfaced.
“The car went down that embankment, which was not very long, and apparently it overturned into the water.
“The mother managed to free herself and got the children out but the father was trapped inside.
“The children may have been knocked unconscious.”
He said Mr Mullan was well-known in the local area as a lot of people would buy their flowers and plants from him.
The victims were taken to Letterkenny University Hospital mortuary where post-mortem examinations will be held.
Gardai are appealing for anyone who was travelling on the road between 10pm and 10.30pm on Thursday to come forward.
They want to hear from anyone who may have seen a Black Mitsubishi ASX, registration number 11 DL 1566, in the area at the time.
