Viewers saw the shocking moment ambulance service call handlers spoke to a caller claiming to be a child whose grandfather had been stabbed to death.
Tonight's episode of BBC One 's Ambulance showed control taking a call from someone who said they were nine-years-old and that two people had been fighting, and someone had killed their granddad.
"Two people fighting and got a knife, and killed my granddad" says the caller.
The caller went on to divulge that the person responsible was still in the house and was aware that they were making the 999 call.
A huge emergency response, including an advanced paramedic, two air ambulances, one ambulance and an incident commander were all scrambled to the scene.
But when advanced paramedic Tim arrived on the scene, he discovered all was not what it seemed.
Despite the scene not yet being declared safe, Tim was so concerned about the possibility of a child being at risk that he entered the house - and found that there was no emergency.
Instead, he discovered a family who seemed shocked to find him there.
Cameras then capture the moment the clearly frustrated call handlers realise the call had been a hoax, before everyone is stood down.
"How many vehicles is that?" One member of staff asks, "Four vehicles two helicopters? Cracking. For a fake."
The latest episode of the BAFTA award-winning documentary also saw crews tackle a number of genuine emergencies during last year's bank holiday weekend.
Will there be another series of BBC's Ambulance?
Over the period, they took more than 18,000 calls.
The episode also captured the moment an air ambulance landed in the middle of the pitch at Lancashire County Cricket Club, after a spectator had a cardiac arrest.
Crews battled to save the man and were eventually able to bring his circulation back to normal, but sadly the patient, who was later revealed to have been called Tommy, died four days later in hospital.
Other cases shown on the episode, which is the last of series four, included groom Simon, who broke his leg playing football two weeks before his wedding.
It also featured 80-year-old Bridget, who took all the skin and fatty tissue off one of her arms and her foot after her own car ran over her in a freak accident, but still stoically managed to laugh and joke with paramedics and police despite the extremely painful injury.
