A San Diego man who organized Bernie Sander’s local Facebook group during the 2016 presidential election told NBC 7 he noticed traces of Russia’s hidden social media trolling campaign years ago.

After Sanders was beat out by Hillary Clinton for the Democratic nomination, he noticed something was a little off.

“Hundreds and hundreds of people were joining Bernie Sanders pages on Facebook for a campaign that was over. It made no sense.” John Mattes told NBC 7.

Mattes resorted to checking other Bernie Sanders pages around the country. “It was everywhere," he said. Mattes noticed that the posts had a similar theme. "‘Anti-Hillary’, ‘Hillary is sick’, ‘Hillary is involved in Al Qaeda’, ‘Hillary’s getting money from the Russians’”.

“I started digging deeper, tried to look at the servers, I tried to look at the IP address of these people,” Mattes added. Soon, he realized that the people behind these accounts weren't actually people.

“I call them at the time ghosts. Really they’re bots, they’re trolls” Mattes said.

Mattes soon caught on to some of their telling signs.

"They would misspell where they’re living in the United States or they would have no profile at all, they were just ghosts."

Mattes said Friday's indictment is just the tip of the iceberg.

”What this indictment does not address, is the bots on Reddit, the bots that worked on Twitter, on Tumbler. There wasn’t a social media platform the Russians didn’t infiltrate," he proclaimed.

Mattes said the bots didn’t have a lot of obstacles and that their system was pretty easy.

“All they had to do was open up a fake Facebook account and then join a page, a Bernie Sanders page, where you find sympathetic people to Anti-Hillary posts and you circulate a vicious post. Pretty straight."

For those who are regular social media users, he says it’s important to stay alert.

"Look at the sourcing. Look at who the person is. Do you really know the person that is inviting you to join a group? Do you know the person who sent an article from RT?”

After a lengthy investigation, Mattes said he took his findings to the Clinton Campaign as well as the Obama Administration last September.