ITV aired a true crime documentary on Thursday evening detailing the tragic and horrific murder of Sadie Hartley.

The 60-year-old mum was shot with a 500,000 volt stun-gun, then stabbed with an eight-inch carving knife in the face and neck, at her her home in Helmshore, Lancashire, in January.

And the one-off programme even saw documentary makers catch this shocking moment – the killer’s arrest.

Moment Sarah Williams is woken in her bed and arrested for the murder of Sadie Hartley (ITV)

Two women – “bunny boiler” Sarah Williams and her accomplice Katrina Walshwere – were convicted of murdering Hartley and were both jailed for life at Preston Crown Court.

The programme followed lead detective Paul Withers on every step of the case, as he worked with his team in the Lancashire Police to uncover the mystery.

Detective Paul Withers (ITV)

The Murder of Sadie Hartley demonstrates how outstanding our Police Forces can be. Excellent investigating to a brutal crime.

— Ash Kennedy (@Ash_J_Kennedy) September 1, 2016

Viewers thought the access ITV and documentary makers Raw Cut TV had been given was amazing – from covering the first 999 call, to interviewing the suspects and following the search for the murder weapon – was such an insight into the work of the detectives.

Incredible work by @RawCutTV and @TVWarr on #sadiehartley programme – best access I've ever seen and a truly compelling film.

— David Prior (@dmhprior) September 1, 2016

How an earth did they get this level of access to a murder enquiry! It's fascinating viewing. 😮#TheMurderOfSadieHartley

— Kate Naylor (@katenaylor191) September 1, 2016

Amazing access & great professionalism by @LancsPolice Shows how vital CCTV & mobile phone analysis are to policing #themurderofsadiehartley

— Mark Williams-Thomas (@mwilliamsthomas) September 1, 2016

Watching #TheMurderofSadieHartley Can't believe how much access these cameras had. Heart goes out to Sadie's family 😔

— DANNIE (@DansGall) September 1, 2016

Excellent to see how the detectives work. #Themurderofsadiehartley

— Jenny (@ladderack) September 1, 2016

Everyone was feeling such conflicting emotions while watching the gripping documentary.

This documentary on The Murder of Sadie Hartley is fascinating yet horrific, the poor woman!

— Mike (@mkb16_) September 1, 2016

The Murder of Sadie Hartley on #ITV is both chilling and interesting at the same time. Awful crime. 😔#SadieHartley

— Andrew Morris (@Moz91) September 1, 2016

ITV documentary on Sadie Hartley's murder is utterly gripping. Terrifying, but incredible telly.

— Nick Reilly (@NickJWReilly) September 1, 2016

This is great, but also incredibly sad #themurderofsadiehartley

— lucy (@lucy_dennett) September 1, 2016

We also saw interviews with Sadie’s daughter Charlotte, 23.

Sadie’s daughter Charlotte (ITV)

She described losing her mother as “numbing” and Twitter found it simply heartbreaking.

What a courageous young woman talking about the impact of her mum being murdered. Unimaginable. #TheMurderOfSadieHartley

— Probation Officer (@PoOfficer) September 1, 2016