John Delahaye, 46, was pronounced dead at HMP Birmingham on Monday just one week before he was due to stand trial over allegations of attacking worshippers at the New Jerulasem Apolistic Church in Aston, Birmingham.
According to Birmingham Live, in 2002, Delahaye from Aston developed a "violent fixation about a solicitor acting for him over a harassment matter", who he believed badly represented him.
He had been removed a number of times from a Birmingham law firm before "vaulting the counter" and repeatedly stabbing a trainee lawyer - twice in the chest, in the head, hand and shoulder.
He was found guilty of attempted murder and jailed for 12 years.
Only two days before last September's church attack, which left a church elder and two other men with injuries, Delahaye reportedly returned to the same Birmingham legal firm and made further threats.
His victim 15 years ago - who didn't want to be named - told Birmingham Live he wasn't surprised by Delahaye's church attack.
"He came across as a man who was cool, calm and calculated. When we ejected him from the office, he didn't run like most would.
"He called the police and made a complaint. That shows a man with brains."
Thanks for all of your messages of support and prayers. I'm recovering well. #LevelUp pic.twitter.com/JcbONF95SH
— Adam Brooks // #LevelUp (@AdamBrux) September 11, 2017
Delahaye was to stand trial on Monday charged with attempted murder, making threats to kill, two counts of wounding with intent and two of possessing offensive weapons.
Adam Brooks, who was injured in the attack, told Premier he had mixed emotions when he found out about Delahaye's death because he thought "the trial would be "the moment of closure".
Delahaye's death is being investigated by the Prison and Probation Ombudsman.
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