A young girl told her family "something's happened" shortly before her best friend was found dead along with her entire family.
The bodies of 11-year-old Maja Wlodarczyk, her dad Michal , 39, mum Monika, 35, and brother Dawid, three, were discovered at their flat in west London on Friday.
Police forced entry to the upstairs property on Staines Road, Bedfont but nothing could be done to save the family.
Detectives said they were not seeking any other suspects in connection with the deaths but were keeping an "open mind".
Friends and neighbours of the victims have since paid tribute to the "lovely" family, who were originally from Poland.
James Hoopa, the father of Maja’s best friend, visited the family home where forensic searches were ongoing to lay flowers with his family.
He told how his daughter, 11-year-old Jasmine Hoopa, ran home to him on Friday afternoon to tell him something had happened to Maja.
Mr Hoopa said: “My daughter goes to school with the little girl in the same year.
"Last night I finished with about half six and I came down here and I saw the police cars and everything.
“I got home and I said well, have you contacted your friend? Is she okay? But you know what children are like, no notice.
"Then I come back from work today I find out that she's dead.
“I found out Maja is dead. We know the parents as well, the dad and the mum, they all go out together. She was just a normal child, growing up, a lovely girl. She’s just a normal child, this is a shock.
"I don’t know how my daughter is going to get through this because my daughter is very best mates with her.
“For her to go through this experience, something else as parents that we’ve got to deal with. We’re neighbours, we live across the road, this is a shock - it’s going to take some time to settle into this one."
His wife Mrs Hoopa added: “Occasionally I’d take them out, just me, Maja and Jasmine would go out together.
"We’d plan to go out, we went to McDonald’s, we went to Nando’s, not long ago we went to Staines shopping.
“This morning she went out. Not long later she came home, I was a bit surprised she came home so quickly.
"She said to me 'mum, mum, something’s happened, I think Maja, something’s happened to her'.
“I said let’s go and check, we saw the article online that they’d passed away.
"Me, Jasmine, and Jennifer, my daughter, we all rushed down to verify because the description matched them. I thought 'no, no this is not right'.
“I just can’t believe it. She was a very brave girl, very mature for her age. It’s just a shock. I don’t know how we’re all going to pull through as family.”
Neighbours also told how they watched Monika playing "very happily" together with her two children just days before their tragic deaths.
Oana Petraru, 31, said she often saw the mum joking and laughing with the children in the evenings and weekends, but rarely saw the dad.
She said: “I just saw the mum because the garden is just out there. I saw her sometimes with the kids outside. They were very happy. She was always playing with them, with the ball, just being a mum, you know?
"There was nothing strange with them. I don't know them personally, but she seemed fine. They were laughing and playing in the garden a couple of days ago, the mum and the boy and the girl."
Detective Chief Inspector Linda Bradley said previously: “I would like to assure the community that specialist detectives are working to establish the circumstances which led to this tragic incident and we will provide further updates as soon as appropriate.
"Our thoughts are with everyone who has been affected by what has happened.
“Our investigation is at an early stage, and the situation remains that we are not currently seeking anybody else in connection with the incident.
“We are however retaining an open mind, and I would ask anyone who feels they have pertinent information to contact us as soon as possible.”
Anyone with information that may assist the investigation is asked to call 101, quoting reference 5135/16Jun. Alternatively please provide information via the online form at: https://mipp.police.uk/operation/01MPS23V28-PO1.
