The family of three children killed by their father in Shropshire have said they "cannot begin to imagine" what was going through his mind.
The bodies of Sam Fuller, 12, and his sisters Becka, aged eight, and seven-year-old Charlotte were discovered in Pontesbury Hill,on Monday.
It is believed they had been stabbed to death by their father Ceri Fuller, 35, who then fell to his death at a nearby quarry.
West Mercia Police have recovered a knife and one line of inquiry detectives are following is that Mr Fuller killed the children before taking his own life.
David Fuller - Mr Fuller's father and grandfather to the children - released a statement on behalf of his and his daughter-in-law's families through police.
"The Fuller and Tocknell families are devastated by this tragedy," Mr Fuller said.
"Ceri was a gentle, sensitive and intelligent man but also a very private one. He loved his children dearly and they were such a focal point of his life.
"His relationship with each one of them was one of gentleness, involvement and attentive nurturing.
"Sam, Rebecca and Charlie were such charming individuals, brought up in an environment of love.
"We cannot begin to imagine what was going through the mind of this gentle man to drive him to such tragic actions.
"We would ask all to respect our privacy at this time while we try to come to terms with this terrible loss."
Earlier, the children's' mother spoke of her devastation.
Ruth Fuller, who had been married to Ceri Fuller for nearly three years, said: "I don't have the words to describe how I feel at the moment. All I would ask is that I be left alone to grieve for my family."
West Mercia detectives have launched a murder investigation but described the deaths as a "tragic family situation" and are not looking for anyone else.
Detective Chief Inspector Neil Jamieson, who is leading the investigation, said: "Officers involved in the search found a knife in the vicinity of where the bodies were found. It will now be forensically examined."
Mr Jamieson said the old quarry and surrounding woodland would remain cordoned off as officers continue a detailed search of the area.
Police are appealing for information about possible sightings of a red Land Rover Freelander and its four occupants on Thursday when Mr Fuller and his three children left their home at Milkwall, near Coleford, in Gloucestershire.
Mr Jamieson said: "We believe this vehicle left Gloucestershire at some point last Wednesday evening or early Thursday morning and we are anxious to establish its movements since then, especially in the Pontesbury area.
"We believe it was in the Leominster area at around midday on Thursday before making its way up towards Welshpool later that day."
Post-mortem examinations will be conducted on Tuesday afternoon by a Home Office pathologist and may not be concluded until Wednesday.