Shaking as he frequently broke down in tears, Dr Russell, 44, talked of the brutal murders and the permanent injuries suffered by his other daughter Josephine, 9, who was left unconscious as she walked home from school with her mother and sister last Tuesday.
Police are still hunting the person who battered 45-year-old Lin and her daughters in a frenzied hammer attack in woods close to their home in Nonington, near Canterbury, Kent.
Dr Russell, who lectures in nature conservation at Kent University, said: "I swing between periods of complete desolation, but most of all I am thinking about Josephine. I want to get her over all of this as soon as possible.
"She is improving almost hourly. Every time I go to see her she is a little better. The doctors tell me she is physically fairly OK. She is off the ventilator. She has got various signs of impairment to her mobility, but I can't tell how bad that will be yet.
"She is awake and she can focus on me. She knows who I am, but she can't talk at the moment. She doesn't yet know that her mother and sister are dead. I can't bring myself to tell her."
The family moved to the Kent village from North Wales last year. Dr Russell said: "To some it was the idyllic life ... Living in a beautiful little listed cottage in the country. Lin had dedicated herself to building up the garden. There were the ponies, the cats, the dogs, walking the dogs in the country. We never once felt afraid.
"The girls were very much country children. They grew up in South Africa and they were both little tomboys. They never needed television or many toys. They had their own amusements.
"The best thing that the person who did this can do for everybody's sake, even for his own sake, is to come forward. I fear for the safety of everybody who he is near. Any animals who he is near. He killed my dog as well as my wife and child."
Dr Russell revealed that, a week before the tragedy, a thief stole a plant pot from the family's garden. "It was the first time we had talked about any possible safety problems," he told a press conference. "I said that maybe Lin shouldn't go shopping every Tuesday and that we should vary our movements to deter anybody from stealing from us again.
"We had lived in South Africa for 15 years, where Josie was born, and Namibia for two years, where Megan was born, and we had never had any problems there.
"Nothing horrid has ever happened to our family before. We have led unusual and exciting lives, we have never had anything tragic touch us. A dog dying is probably the most tragic thing we have had to face."
Mrs Russell and her daughter would be buried in the countryside of north Wales which they loved so much, said Dr Russell. Clutching a police liaison officer's hand, he said: "It's what Lin would have wanted, it's what Megan would have wanted and and it is what me and all my family want."
Dr Russell said of Josie: "She may be able to sketch the man we are looking for. She is a very good drawer, she gets that from me, but I don't relish the thought of having to go through that with her. I don't know whether I will be able to stay in Kent. It's a very idyllic part of Britain. But I returned to my house for the first time last night and the lanes and the trees and the garden look very different now."Reuse content