The grisly murder in the holiday island has made headlines after a couple found the boy wandering on the mountain earlier this week, bringing him to police whom he reportedly told his father had assaulted his mother and brother.

His 43-year-old father was detained on Tuesday evening in Adeje in the southwest of Tenerife, in the Canary Islands.

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Police launched a major search and on Wednesday found the bodies of the 39-year-old woman and her 10-year-old son “in a mountainous area, inside a cave, between two ravines,” police said.

The suspect was “taken to an investigating magistrate” at a court in Santa Cruz de Tenerife for questioning, a police spokesman told AFP.

The central government's representative in the Canary Islands, Juan Salvador Leon, told reporters he was “sure that it was premeditated, that he had planned to trick his sons and wife.”

'Hidden Easter presents in a cave'

A Dutch woman in the area who helped translate between the seven-year-old and investigators, told reporters the family had “gone up via a path” as if they were going on a walk.

“It appears they had a picnic and that the father then said he had hidden Easter presents in a cave and he took them there, tricking them,” said the woman, identified as Annelies by Spanish media.

She says the boy said he saw his father beat his mother and then attack his brother.

“The kid doesn't know that his mother is dead” but believes she is “just seriously injured,” she told reporters.

He “was really intelligent, he threw a stone at his father and ran away, the father wasn't able to catch up with him.”

According to Spanish media, which cites sources close to the probe, the mother and children were visiting the father who lived in the Canary Islands.

The parents were separated, media said.