Derbyshire Police said their mother, 35-year-old Terri Harris, and Lacey’s friend Connie Gent, 11, were also found dead at the property on Sunday (19 September) morning.
Bennett stayed at the scene for more than half-an-hour on Monday, clearly distraught and being comforted by a friend or relative.
Asked about his feelings as left, he said “heartbroken; million pieces; shattered”.
But what happened in Killamarsh, and where is it located?
Here is everything we know.
What happened in Killamarsh?
Derbyshire Police said they were called to the house at around 7.25am on Sunday (19 September) and found the bodies of four people.
At around 1.30pm, police made the public aware that they were dealing with a “serious incident” in the town, the Derbyshire Times reported.
On Monday morning, Chandos Crescent remained sealed off with a number of police officers patrolling the street and many police vehicles parked in the surrounding streets.
The house is semi-detached, of a prefabricated design, with a large playing field on one side, which was also cordoned off. There was a blue police tent in the front garden and forensics officers were conducting inquiries.
Around 300 people gathered on Monday evening for a vigil in a park a few hundred yards from the police cordon, where they placed candles, flowers and teddy bears.
Many people were in tears as they stood and listened to prayers from Killamarsh street church pastor David Taylor.
Derbyshire Police said a 31-year-old man has been arrested on suspicion of murder and remains in police custody, and they are not looking for anyone else in connection with the deaths.
Officers did not have any prior contact with those involved, police added.
Detective Chief Inspector Rob Routledge, who is leading the investigation, said on Sunday evening: “We would really like to hear from anyone who saw or heard anything suspicious in the early hours of this morning, or has any information which they think could help with our inquiries.
“No matter how small you think that information may be, please do get in touch with us.”
Chief Constable Rachel Swann urged any witnesses to come forward, saying: “A team of detectives have been working through the night to understand the circumstances that led to their deaths and I would urge anyone with any information to come forward.
“Of particular interest is anyone who was in the Chandos Crescent area between 9.30pm on Saturday evening and 7.30am the following day and who may have information that would be helpful to the investigation.”
Where is Killamarsh?
Killamarsh is a town in North East Derbyshire, bordering Sheffield and South Yorkshire to the north-west.
Situated on the eastern side of the Rother Valley, Killamarsh is roughly the same distance to the centres of Sheffield, Chesterfield and Rotherham.
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