Detectives were tonight trying to establish a motive for why a devoted husband and father would kill his "perfect family" before taking his own life.
Richard Smith is thought to have killed his wife Clair and their children Ben, nine, and Aaron, one, before taking his own life at the home they shared in Pudsey, near Leeds.
Police have launched a murder inquiry, but have said they are not looking for anyone else, after the bodies were found in a fire-damaged upstairs bedroom yesterday afternoon.
Mr Smith, 37, who worked for a shopfitting firm, and his 36-year-old wife are thought to have moved into the modern stone-built house a few months ago.
The tragedy appears to be another incident involving a father killing his family. It is thought there is no obvious motive for Smith's actions.
The bodies were removed from the house and taken away in a private ambulance today. Officers are trying to establish how each family member died.
Relatives and neighbours spoke of their shock as news of the killings became public.
Family friend Sara Turnbull was in tears as she left flowers at the police cordon.
The message on her bouquet said: "You were such a beautiful family. All our love to you. We can't believe you are all gone."
Her husband Dean said the families had known each other for 15 years and been on a number of holidays together.
Mr Turnbull said: "We can't take it in. All we know is they are a lovely family, lovely two kids and we're in shock.
"We hadn't seen them for a while but we saw them last week. I went out for a drink a week or so ago and I saw Richard and Clair out.
"I said we'll come round and see you. We haven't seen you for a while.
"We went to their new house and it was superb. Brilliant. We really enjoyed ourselves."
Mr Turnbull said: "There was no sense of any problems."
With the Turnbulls was another friend, Sheral Heights, who said the Smiths were her son's godparents.
She was in tears as she left flowers, saying she was "devastated" but did not want to say any more.
Mr Smith's cousin Gary Tempest said: "It is so unbelievable this has happened.
"They were the perfect family."
Asked whether Mr Smith could have hurt his family, Mr Tempest said: "I don't believe that for a minute.
"He thought the world of them."
He said his cousin was football mad and had no money worries. He said they both had good jobs. It is thought he coached junior football teams.
"I've known Richard all my life. There's never been any bad things - arguing or anything."
Friend Sarah Wilson was in tears as she laid flowers.
She said: "I can't imagine what's made this happen, I really can't.
"I just can't believe it, I just can't."
She went on: "They were just ordinary. I'm making that sound like a bad thing, and it's not."
She said she once held Aaron in her arms as her sister was a neighbour, and added: "Such beautiful little boys. Both of them."
Ms Wilson continued: "They were just like anybody else. Just fine.
"There was just no inkling that anything like this would happen. Nothing."
Part of Sheridan Way where the house is located was initially cordoned off amid fears that dangerous chemicals might be present.
The tragedy comes just days after a police officer who had been dismissed by his force attacked his family before apparently killing himself.
Toby Day is thought to have killed his primary school teacher wife Samantha and youngest daughter Genevieve, six, in a frenzied attack at their home just days after he was sacked by Leicestershire Police.
Day also attacked their other children Kimberley, 15, and Adam, 13, before taking his own life at their home in Melton Mowbray, Leicestershire, on Thursday.
Inquests into the deaths were opened and adjourned by a coroner today.
Kimberley and Adam were taken to Queen's Medical Centre in Nottingham where they remain in a stable condition.