"They were very professional ... it all looks genuine."
The scam began with a cold call from someone probably based in a country such as Singapore, Hong Kong or China, who offered shares in a legitimate sounding company, Mrs Flower said.
"It appears to be fairly genuine, they will go with a known brand, something that you can look up and it looks genuine.
"They get quite close to known names, like Meyer, which is a big financial company but they used Meyer Global, which is not real."
The scammers used a "hidden website" which concealed the location of the website and any contact details, as well as frequently changing IP addresses.
They followed up with emails on letterhead from legitimate sounding email addresses.
Masterton Police were alerted to the scam when the man's bank picked up on two deposits to a Singapore account and asked him to contact police, Mrs Flower said.
The scammers told the man his investment had increased eight-fold, but he would need to pay thousands in order to take his money out.
"It started with a small investment ... but he'd been sucked in and sucked in.
"If he'd kept going the way he was he would have lost his house.
"He doesn't have the money to give away. He is a widower now, so he's looking after family members as well, which he can't now be as supportive of as he would've liked, and he feels a bit like a fool -- his pride has taken a huge blow."
The scam was professional enough to fool anybody, Mrs Flower said, but a good guiding principle was "if it seems to good to be true it probably is".
Police urged anyone who received a similar cold call to be on their guard.
"Be aware of people calling for investments -- that isn't the way it happens, and don't invest any money without checking that information out."
Scamadviser, Netsafe were good places to start for quick advice on the legitimacy of websites, she said.
The scam had been referred to Interpol and it was hoped the man's bank might be able to retrieve one of his deposits.
Anyone who had taken in by such as scam should contact police, Mrs Flower said.
"There's not a lot we can do to get your money back but we can use the information to prevent further incidents and pass the information on to Interpol."