A pensioner repeatedly bludgeoned a 68-year-old colleague with a lump hammer in an unprovoked attack at the day centre where they worked.
Stephen Newman (72) was jailed for six years for the attack, which happened while his victim was sitting down drinking coffee and reading a newspaper.
The injured man needed 78 stitches to nine head wounds.
His wife, a nurse, said after the hearing at Leicester Crown Court: "My husband is now a changed man and has had to give up his job.
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"He harbours no ill-feelings about what happened. I think justice has been done.
"The attack defies logic and there was no reason for it at all."
Newman, of Gedding Road, North Evington, Leicester, was a maintenance worker, at the Douglas Bader Day Centre, in Malabar Road, St Matthews, where the attack took place.
The victim, a receptionist, had worked with Newman for eight years and they had not fallen out.
Newman pleaded guilty to wounding with intent, on June 5.
Sentencing, Recorder Adrian Reynolds said: "You attacked a man who was himself elderly.
"You had no obvious grievance and the circumstances of this attack are bizarre.
"A doctor's report says you were probably suffering from a depressive episode at the time.
"It may be you were going through some difficulties which impelled you to behave in this way which defies understanding.
"You armed yourself with a lump hammer. It had a very substantial head on it and set about attacking him repeatedly to the head.
"It was a miracle he didn't suffer any fractures.
"The rest of his life will be affected by what you did to him."
Victoria Rose, prosecuting, said the victim arrived for work at 7.45am and was sitting reading a paper.
She said: "He suddenly felt a blow to the back of his head and three more blows followed.
"There was a brief pause and several more blows. The complainant asked 'What are you doing?'
"He was bleeding heavily and the defendant said 'sorry'."
Newman attacked him again whilst also calling out for help, saying: "He's bleeding."
The defendant then began rambling incoherently and expressed suicidal thoughts.
He said he found the hammer at the centre that morning but could not remember the attack.
Sarah Cornish, mitigating, said that Newman, who is registered blind and does not have a history of violence, appeared "confused".
A psychiatric report stated he was under stress at the time.
