Two brothers from Sydney’s south west are accused of one of the lowest acts imaginable, stealing the life savings of an 88-year-old man with dementia.

It’s alleged the pair gained access to the elderly man’s bank accounts and stripped them of more than $600,000 over the space of a year.

WATCH THE VIDEO ABOVE: Brothers accused of stealing $600k from dementia victim

Know the news with the 7NEWS app: Download today

Moving in before dawn, police arrived to arrest 22-year-old George Mensah and 25-year-old Jesse Mensah at their Yagoona unit.

The brothers are accused of preying on one of our most vulnerable. The victim has dementia.

Police say he received a cold call last year. He thought it was from his bank, convincing him to share his account logins.

“Some of the calls lasted 90 minutes and the men depicted that they were employees of his bank,” Detective Superintendent Gordan Abinja said.

“This man was completely exploited and stripped of all his wealth.”

The two men were arrested on Thursday. Credit: NSW Police

Over the course of a year, the pair is accused of fleecing $600,000 from his savings and credit cards, transferring stolen money to their own accounts before buying shares in an alleged bid to launder that money.

“I consider targeting vulnerable people the apex of offending,” Abinja said.

Police wouldn’t name the bank at the centre of this scam but today thanked its fraud team for helping to crack this case. It’s understood it was CommBank.

Police moved in before dawn. Credit: 7NEWS

And the good news is that after all this victim has been through, every dollar stolen from him will now be refunded.

“The bank has reimbursed the victim of all his money, and I commend them for that conduct,” Abinja said.

The two will walk free on bail on Thursday. Police say they’re still looking for two others allegedly involved.

“Everyone has elderly family members. If you can, try to get some legal guardianship over their finances. Be vigilant in relation to their spending,” Abinja warned.