Det Supt Tom Chisholm, head of the West Midlands Police homicide investigation team, and a detective with 22 years experience, confessed: "It is the most shocking case I have ever dealt with because of the unpredictable level of violence.
"There was no build up to it. It was completely unexpected and it is very unusual for there to be no clear motive for a crime of this magnitude.
"It is also incredibly rare for there to be an attack on a family at their home like this. Those who died and their family will remain in our thoughts for many years to come."
Aaron Barley, who was known to police and social services, refused to be interviewed or to give blood for drink and drug analysis.
"This was a truly shocking incident," said the officer. "Clearly we deal with murder – it is our job, we deal with it on a daily basis.
"It is incredibly rare that we deal with an incident that has such a massive impact both on the victims’ family and the wider community, and indeed officers that investigated it."
He praised the courage of Peter Wilkinson in raising the alarm despite being stabbed six times, and explained: "Officers arrived with paramedics and found Peter Wilkinson with serious injuries. They entered the house itself and found Tracey upstairs. Sadly, she was already deceased at that time.
"They also found Pierce who again had significant injuries. He was taken to the Birmingham Children’s Hospital and worked on while en route. Tragically, he passed away shortly after arriving.
WATCH: Lydia and Peter Wilkinson and leading police speak of the 'shocking' killings
"Quite incredibly Peter was able to tell us who had attacked him at his home, and it was apparent that the family vehicle had been stolen."
Barley, who was uninjured in the carnage, was arrested after being spotted driving the family's Range Rover, which he crashed into a wall near the scene.
Mr Chisholm concluded: "Efforts were made to interview him but he remained largely uncooperative throughout his time in police custody.
"He still has not assisted us to gain a clear understanding of what motivated him or what the reasons were behind this horrific attack."
Barley's parents both died when he was young. There was a suggestion that his mother had a drink problem.
He escaped from a children's home when he was 13 and spent a short space of time being fostered by a family in Stourbridge.
The 24-year-old had a chaotic lifestyle, was rumoured to have worked as a rent boy and had previous convictions for violence, although nothing on the scale of what happened at Greyhound Lane, Stourbridge on March 30.
Mrs Wilkinson and her 13-year-old son Pierce were buried together at St Mary's Church, Oldswinford on June 7. Her daughter Lydia told the congregation: "They were as close as a mother and son could be. They shared a bond of love that could never be broken."
Mr Wilkinson concluded: "My wife was a beautiful woman with a heart of gold. She was stylish and elegant, very compassionate. She cared for others and it is just so tragic that, after trying to help Aaron, that he should turn on us in this way for no apparent reason."