A teen who slayed his family "seemed like a really chilled person" and "didn't give off a vibe" before killing his mother and two siblings , a neighbour has claimed. On Monday, Nicholas Prosper, who is now 19, pleaded guilty to the murders of Juliana Falcon, 48, Giselle Prosper, 13, and Kyle Prosper, 16, at Luton Crown Court. Their bodies were found at a flat in Leabank, off Wauluds Bank Drive, Luton, Bedfordshire, on September 13 last year. He was also planning a shooting at St Joseph's