Unseen footage of police responding to a triple murder will feature in the Channel 4 series 24 Hours in Police Custody.
Nicholas Prosper used a shotgun to kill his mother Juliana Falcon, 48, his brother Kyle, 16, and his 13-year-old sister, Giselle, at their home on 13 September 2024.
Footage shows the dramatic moment police use stun grenades as they enter the flat at Marsh Farm in Luton, finding the three victims inside.
The documentary, which follows the work of investigators at Bedfordshire Police, will feature the case over two nights on 5 and 6 October.

