A man who stabbed his ex-girlfriend and their young son to death was arrested for threatening to kill them a week earlier, it has emerged.
Andrew Cairns, 44, stabbed Rachael Slack and 23-month-old Auden before turning the knife on himself in the sleepy village of Holbrook, Derbyshire, on Wednesday.
Miss Slack, 38, was three months pregnant by her new boyfriend, and friends said she was the "happiest she had ever been" after starting a new life with the unnamed man following the breakdown of her relationship with Cairns.
As he stabbed Miss Slack and Auden to death, the mother could be seen "screaming in terror" from a downstairs window at the Victorian cottage in Well Yard.
Auden's parents were found dead but he was still alive when the emergency services broke in. The toddler was taken to hospital by air ambulance but died later from his injuries.
The Independent Police Complaints Commission is deciding whether it will carry out its own investigation after a friend revealed that Cairns was arrested last week for making threats to kill his estranged family. The watchdog said it was deciding its level of involvement in any investigation into mistakes made by police.