A German woman and her son were found dead in a cave on the Spanish holiday island of Tenerife, authorities said.
The boy’s father was arrested after another of the couple's children - a five-year-old boy - fled and raised the alarm.
A search found the bodies of the 39-year-old woman and the 10-year-old near Adeje in the southwest of the island.
Spain's prime minister, Pedro Sanchez, commented on the apparent attack as he campaigned ahead of Sunday’s national election in which violence against women has been a voter issue.
"A woman and her son were murdered, once again macho violence hit," he wrote on Twitter. "We have to end that."
A spokesman for the local Civil Guard said: "The bodies were discovered in a mountainous area, inside a cave, between two ravines. Apparently, the five-year-old had managed to escape … and people found him in the mountains and warned the civil guard.”
He said the causes of the two deaths were yet to be established. However, the German Press Agency on Thursday reported that the mother and child "were brutally beaten to death in the cave," according to a spokesman for investigators.
Jose Miguel Rodriguez Fraga, mayor of Adeje, told reporters that the surviving boy was "in shock."
"We don't have much to go on," he said. "It seems that the father was living here, the mother would come and go. And this was one of the times she was visiting, when all this happened. Yesterday they were out for a walk, and all this rather strange situation occurred."