A TEENAGE gunman who killed his friend and drew up a hit list of people he wanted to shoot has been detained in a mental unit indefinitely.

And today the family of Mark Harrington's victim demanded answers about the way he was treated in the psychiatric unit at Blackburn's Queen's Park Hospital before the shooting.

Harrington, who has a history of mental illness, shot 18-year-old Anthony Rigby once in the back of the head at his Swift Close flat, Larkhill, Blackburn.

Anthony, described by Judge Peter Openshaw as blameless, died from his injuries four days later in Royal Preston Hospital.

Preston Crown Court was told 20-year-old Harrington, who was 19 at the time of the shooting, drew up the list and chillingly warned he would "blow away" his friends "one by one" after developing irrational grievances.

On the top of the list was Anthony Rigby. After the case, Det Supt Ian Jones, said Harrington was more than capable of killing all those on the list.

Harrington, who pleaded guilty to manslaughter on the grounds of diminished responsibilities, had been receiving treatment at Queen's Park Hospital's psychiatric unit as an out patient for a number of years.

As he was detained under the Section 41 of the Mental Health Act, bosses at Blackburn, Hyndburn and Ribble Valley Health Care NHS Trust said they had launched an investigation into how the tragedy happened.

A serious incident internal review was set up by acting chief executive, John Thomas, following the shooting on January 7, 2002. A report, which will contain a number of recommendations, is expected soon.

Anthony's mother Carole, of Corwen Close, Blackburn, said: "I want answers from Queen's Park to find out why they ever let this scum ever walk the street. This will never be over. I'll get justice for Anthony and do everything in my power to never let Harrington walk the street. He has taken so much away from us -- our Anthony."

The court heard that Harrington, of St James Road, Blackburn, had known Anthony for a number of years.

Richard Marks, prosecuting, said that as a teenager Harrington began to display examples of "bizarre behaviour." He would accuse Anthony and the other friends of flicking cigarette ash in his hair.

Last year Harrington, Anthony and another friend were sitting in a car after a night out in Blackburn, when Harrington produced a large knife from under the seat, and held it at Anthony's throat, causing a deep cut.

On Sunday, January 6, the day before Anthony's death, Harrington rang him at his flat asking if he could have a bath. Anthony refused and spent the day with a friend, drinking and watching television. His friend left at between four and five on Monday morning.

At 11.30am Carole Rigby entered her son's flat and discovered his body in the blood-splattered front room.

Surgeons removed a bullet from the back of his brain, which proved crucial in linking Harrington with the crime.

Police stopped him the next day driving in his BMW and recovered the weapon.

Psychiatric experts compiled reports on Harrington and agreed he should be detained.

Judge Openshaw likened the detention to a life sentence and told Harrington: "Your mental illness formed a number of disillusions about him and others, and irrational grievances. You killed him with some ingenuity and have shown no regret, that being in itself further symptoms of your illness."

After the case, Det Supt Ian Jones said: "Harrington has a severe mental disorder and this sentence will allow him to be treated and monitored. The victim's family understands that."

Anthony's mother added: "I will never have any forgiveness ever for him or his family. I have wanted to give up so many times but I had to stay strong to get justice for Anthony.