UK gunman family will row emerges

A grudge held by crazed UK killer Derrick Bird against his twin brother over his father's will may have sparked a massacre which left 12 people dead in northern England.

He was apparently resentful about his brother David getting STG25,000 ($A43,000) from his father Joe when he snapped.

After killing his brother and family solicitor Kevin Commons, 60, it took the father-of-two just an hour to kill 10 more people as he fired bullets from the window of his taxi at seemingly random passers-by.

The frenzied 72km trail of destruction across Cumbria finally came to an end in remote woodland when Bird killed himself.

Joe Bird gave David STG25,000 ($A43,000) before he died in October 1998 at the age of 82, his will, obtained by the Press Association, revealed.

Neither the killer nor older brother Brian appear to have received anything and the rest of their father's wealth passed to their mother Mary, who is 90 and very frail.

Police said on Friday they were investigating claims Bird was in dire financial straits and facing jail over a mystery STG60,000 ($A104,000) being probed by the taxman.

The focus will now move to whether tensions over his father's payout to David angered Bird, pushing him over the edge as his problems mounted.

A legal expert said Mrs Bird would have had to decide whether to include clauses in her own will cutting David's inheritance to allow for the money he had already received.

The revelation added weight to the theory the gunman snapped after rowing with his twin brother about his mother's will.

Last night Joy Ryan, 60, whose ex-husband is Bird's cousin, said the twins were inseparable when young, always playing together in the picturesque village of Ennerdale where they grew up.

But she added that as they grew older the pair also grew apart.

"Derrick would have his own local and David would have his local," she said.

"David was a chap who treated you like an old friend, and even if you only saw him two or three times a year, it was as if he only saw you yesterday, like a really good friend. Derrick was always shy."

It is also thought the gunman was struggling financially - possibly due to an unpaid tax bill.

Mark Cooper, who knew Bird for 15 years, said: "He said, 'They have caught me with STG60,000 ($A104,000) in the bank, the tax people'. He just said, 'I'll go to jail'.

"He just asked me if he could handle jail. He didn't want to go."

Detectives believe Bird had motives for the first two killings and possibly those at his Whitehaven taxi rank. However, it then appears he drove through the once tranquil countryside blastinginnocent people going about their everyday lives.

Yesterday Cumbria Chief Constable Craig Mackey defended his force against allegations they could have done more to stop the killings. "At no stage did any police officer have the chance to end this any sooner," he said.

Mr Mackey revealed that the massacre began in the early hours of Wednesday when the taxi driver shot his brother at his home in Lamplugh.

But police were not called until 10.20am when neighbours of Mr Commons heard shots fired at his home in Frizington. As Bird drove through single-track country roads, police desperately chased him using helicopters, sniffer dogs and mobile phone tracking, but only caught up with him after he had killed another 10 people and taken his own life.