An elderly man has allegedly been bashed with a cricket bat while trying to stop a thief stealing from a charity bin in Melbourne’s Mentone, with the terrifying ordeal caught on camera.

The 75-year-old victim was repeatedly struck by an alleged thief armed with a cricket bat after catching him stealing from a Salvos charity bin on Monday night.

WATCH THE VIDEO ABOVE: Elderly man bashed after catching charity bin thief

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The vulnerable man begged for mercy but was instead allegedly bashed, falling to the ground and suffering a concussion.

“He was laying on the ground, like screaming for help. He looked very injured,” witness Brandon Veza said.

“He was crying on the ground saying, ‘this has broken my spirit and nothing breaks my spirit’,” witness Alexandra Arvanitis added.

Police say the elderly man had taken photos of the thief, which the attacker didn’t like, leading to the violent assault.

A 75-year-old man was repeatedly bashed with a cricket bat after catching a thief stealing from a Salvos charity bin in Mentone. The terrifying attack was caught on camera, but brave tradies stepped in to turn the tables on the attacker. Credit: 7NEWS

The 75-year-old man suffered a concussion. Credit: 7NEWS

“To attack a 75-year-old man who is completely helpless, just trying to do the right thing, reporting to police about a robbery. Yeah, I think it’s really, really cruel behaviour,” Veza said.

Veza and Arvanitis called triple-0 as two tradies stepped in to help.

The attacker tried to walk away, dropping the bat, but then the tables turned.

One of the tradies grabbed the bat and used it on the attacker before making a citizen’s arrest, while the victim watched on in pain.

“He was just saying, please don’t leave me. Please call my wife,” Veza said.

A tradie grabbed the bat and used it on the alleged attacker. Credit: 7NEWS

The tradies then performed a citizen’s arrest. Credit: 7NEWS

The 75-year-old was taken to hospital and 30-year-old Damian Adams was arrested.

Police say he had four outstanding warrants and is also accused of attacking another elderly man earlier this year.

The victim’s wife came to the Salvos on Tuesday morning, sticking a sign to the window thanking “those beautiful, strong, good Samaritans” who she says saved her husband’s life.

He is now at home recovering, while Adams remains behind bars after being refused bail on Tuesday.