The police watchdog has been called in to investigate after a woman was found dead after a "frenzied attack".
Katie Higton, 27, was killed in a suspected double murder alongside her boyfriend in Dalton, Huddersfield, West Yorkshire.
The mum-of-four and her boyfriend were found by police at 9.53am yesterday suffering serious injuries in what police described as an "exceptionally serious offence" with a "bladed weapon".
A 34-year-old man was arrested on suspicion of murder and remains in custody.
Today, West Yorkshire Police said they had referred themselves to Independent Office for Police Conduct (IOPC)
Sarah Lancashire feared telling TV bosses about 'debilitating depression battle'A force spokesperson said: "Owing to police contact with parties involved prior to the incident, a referral has been made to the IOPC."
An IPOC spokesperson said: "We have received a mandatory referral from West Yorkshire Police linked to the suspected murder of two people in Huddersfield.
"This is due to the fact officers had contact with both victims, and a man who has since been arrested on suspicion of murder, in the days prior to this tragic incident.We will now assess the available information to determine what further action may be required.Our thoughts are with all those affected by these events."
Steven Harnett, 25, was named as the second victim of the double murder.
A neighbour told the Mirror: "He had a heart of gold. He was always outside his house."
Katie Higton's ex-brother and sister-in-law placed flowers on behalf of her two eldest children at a police cordon close to where she was killed.
The man, who did not want to be named, said: "Katie was an incredible mum, loving, caring and she absolutely doted on her children.
"It's an incredibly upsetting and distressing situation for her family and children.
"She was a well-loved character within the area. We're all absolutely devastated and so are her children."
The woman told reporters at the scene: "She was so funny, so lovely, she was the most amazing mum, she absolutely loved her children.
'I cleared £15,000 debt by transforming my finances - here's how I did it'"She was a very big part of our family, she was a really good person, she cared for everyone.
"She didn't deserve this. We're all extremely heartbroken and in shock at what's happened and we don't know how to deal with it."
The mental health nurse had been out to the cinema the night before while her mum stayed home to watch the kids, locals told the Mirror.
A local said: “Apparently it was a frenzied attack. It’s just shocking and I can’t get my head around it.”
Tributes left at the scene described Katie as an "angel".
One read: "To Katie, RIP my darling we love you no more suffering, remembered always."
A second said: "Katie, I am so sorry for how things have ended I can't believe it."
A third added: "RIP angel, memories forever, treasured forever and never forgotten."
Neighbours today told of their shock at the grim incident after emergency services flooded the street yesterday.
One said: "I really can't believe it. This area 20 odd years was unpleasant, but over the last decade or so it's gone really nice.
"You don't expect a murder in your street, certainly not a double murder.
"I'm shocked, but it makes sense because there were forensic vans, and an air ambulance and it was swarming with police yesterday."
A police spokesperson said today: "The Homicide and Major Enquiry Team is continuing to pursue a wide range of active enquiries into the murder of Katie and Steven at a house on Harpe Inge in Huddersfield overnight between Sunday (May 14) and Monday (May 15).
"While formal post mortems are yet to be conducted both victims had received multiple injuries believed to have been inflicted by a bladed weapon.
"Specially trained officers have been supporting their families today and
would ask their privacy is respected at what is clearly a dreadful time.
"Police activity remains ongoing at nearby locations to Harpe Inge as part of enquires connected to the murder and local NPT officers continue to conduct reassurance patrols."
Anyone who can assist in the investigation is asked to contact the Homicide and Major Enquiry Team on 101 referencing police log 408 of 15 May.
Information can also be given anonymously to the independent Crimestoppers charity on 0800 555 111.