A father murdered his two young sons and then attempted suicide as he drove at speed into a wall with a makeshift noose around his neck, police believe.
The bodies of Eoghan Chada (10) and his younger brother Ruairi (5) were discovered in the boot of their father's wrecked Ford Focus car following a massive search for the missing boys.
Police in the Republic believe they died at the hands of their stay-at-home father Sanjeev Chada (43), who was discovered injured at the scene near Westport, Co Mayo, with a makeshift noose around his neck.
It is understood the brothers may have died by suffocation or strangulation but gardai are awaiting autopsy results.
The boys had disappeared after leaving the family home in Ballinkillen, Bagenalstown, in Co Carlow, on Sunday night.
They were the subject of a nationwide search amid fears that Mr Chada had abducted them after telling his wife, nurse Kathleen Chada, that he would take them bowling.
Gardai issued the first ever national amber alert for missing children after he failed to return home with them.
Gardai said they had no knowledge of any breakdown in relations in the family.
Mr Chada, who ran a small computer business, was at the centre of an investigation into the alleged embezzlement of €50,000 (£43,000) from a local organisation in Co Carlow.
Mr Chada was last night brought to Mayo General Hospital in Castlebar but his injuries are not thought to be life-threatening.
Gardai have also confirmed that Mr Chada is in an "extremely distressed" state but said they intend to arrest him on suspicion of murder when doctors say he is fit enough to be discharged.
The bodies of the two children were discovered when gardai had gone to investigate a crash at Cloneen, Rosbeg, about 7km from Westport, at around 3pm. Witnesses described how the car had careered down a by-road at speed before crashing into a wall.
"He was travelling at speed and hit the wall. It looked intentional. Locals heard the bang and came out to investigate. The Guards were on the scene within five minutes."
Eoghan and Ruairi were described as extremely popular and "two little sports fanatics".
Father Declan Foley, parish priest near their home in the tight-knit village, was with the Chada family when news of the car accident was broken to the boys' mother and other relatives.
"It was like an earthquake hit the place. It was devastating for all of us," he said.