SLEEPOVER killer Damien Bendall has allegedly left a prisoner fighting for life after battering him with a claw hammer.
The fiend, who killed his pregnant lover and three kids, is said to have smashed the inmate’s skull in a jail workshop.
Sources said the victim was bludgeoned three or four times and may not survive.
Police were investigating Friday’s alleged attack at Frankland Prison, Co Durham.
A source said: “This is a shocking and horrendous attack even by the standards of Frankland, which is a grim and violent place.
“The prison officers and medics who attended were traumatised.
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“Police will investigate it as either attempted murder or murder, depending on whether the victim survives.
“Bendall has been put into a segregation unit.”
In December 2022, Bendall, 34, was given a whole-life tariff for killing his four victims the previous year at a house in Killamarsh, Derbyshire.
He murdered Terri Harris, 35, her son John Bennett, 13, daughter Lacey Bennett, 11, and Lacey’s sleepover pal Connie Gent, 11, with a claw hammer after a drugs binge.
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Bendall also admitted raping Lacey “as her life ebbed away”.
The evil killer then callously called the police to tell them he had murdered four people - before meeting them outside the home to ask for a cigarette.
His trial at Derby Crown Court heard how Bendall and Terri had met online about 18 months before the killings.
The couple's relationship was said to be categorised by his drug use and unstable behaviour and family said they "witnessed in effect a disastrous effect on Terri's wellbeing".
It later emerged he had convictions for violent offences, and an ex-partner had made allegations of domestic abuse.
Last night the Prison Service said: “We cannot comment on a live police investigation but prisoners who are violent face tough punishments.”
Durham Police said: “An investigation is under way.”