This is the moment a man shoved a defenceless pensioner to the ground after complaining the library was 'too noisy' for him to read.
Michael Johnson, 37, shouted at the 80-year-old stranger before using both hands to give him a forceful push outside the public library.
The man's wife and members of the public are seen running to his aid as Johnson continues to yell at the group from the library's entrance.
The man was left with a deep cut to his forehead and pain in his hips and arms.
Police said there had been no interaction between the pair before the attack. Johnson was later tracked down and arrested as he tried to leave the city.
During police interviews, he initially refused to comment before later admitting the assault and blaming it on his mental health.
Michael Johnson, 37, shouted at the 80-year-old stranger before using both hands to give him a forceful push outside the public library (pictured)
The man's wife is seen coming to his aid after he hit his head on the concrete
Johnson (pictured) said he became frustrated because it was too noisy in the library to read
During police interviews, Johnson (pictured left) initially refused to comment before later admitting to the assault which he blamed on his mental health
Johnson said he became frustrated because it was too noisy in the library to read.
Detective Sergeant Joshua Bliss said the man's injuries could have been worse.
He said: 'This is a senseless attack where Michael Johnson attacked a man in his 80s, causing him to suffer a serious facial injury.
'The victim was unknown to the suspect and they had no interaction before the assault. The victim didn't even look in the suspect's direction before he was approached and attacked.
'The suspect has not provided any reason for the attack, other than that he is struggling with his mental health and had been frustrated about noise in the library.
'The victim is vulnerable by virtue of his advanced years, and so his injuries could have been significantly worse.'
DS Bliss thanked witnesses who jumped into action following the assault.
'I would like to convey my huge thanks to the multiple members of the public who witnessed the attack and immediately intervened by chasing the offender away.
'These same members of the public provided vital first aid to the victim until emergency services arrived.
'I also want to thank the local businesses within Salisbury city centre, who supported our investigation by allowing us access to their CCTV systems, which enabled us to track the suspect's movements and obtain a clear image of his face.
'This huge support from the community gave us the tools to swiftly track Johnson down and arrest him.'
Johnson, of no fixed address, pleaded guilty to assault occasioning actual bodily harm at Swindon Magistrates' Court.
He is due to be sentenced on October 21.