At least six threads on 4Chan wrongly named democrat Geary Danley as the shooter and Google showed them in people's search results.
Google typically shows news stories from credible sources. The company announced on Monday that it plans to make some changes to the types of stories it chooses to surface in its results.
50 people have died and more than 200 are injured after the deadliest mass shooting in US history took place on Sunday night in Las Vegas, Nevada.
The gunman has been identified by the authorities as Stephen Paddock. Paddock opened fire from the 32nd floor of the Mandalay Bay Casino, aiming into a close-packed crowd of many thousands of people below, who were watching a country music festival.
One publication, The Gateway Pundit, ran a now-deleted story where it said Danley murdered at least 20 concertgoers.
Danley's name is also being circulated by far-right Twitter accounts. He is being called a "neo-liberal" and "alt-left".
Google did not immediately respond to Business Insider's request for comment.
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The @gatewaypundit wrote up Geary Danley as the #mandalaybay shooter and then deleted their post. pic.twitter.com/ocXtTOX6rL
- Ryan Broderick (@broderick) October 2, 2017