Beto O'Rourke's campaign manager responded to a conspiracy theory that the gunman who perpetrated the mass shooting in Odessa, Texas, last week was an O'Rourke supporter, noting that the baseless claims was amplified mainly by bot accounts. Anthony Shaffer, a former Defense Intelligence Agency officer and a member of President Trump's 2020 campaign advisory board, also promoted the theory on Twitter.

"This weekend, a right wing bot network spread the completely false rumor that the Odessa shooter had a Beto sticker on his car. This was even echoed by Trump advisors," O'Rourke campaign manager Jen O'Malley Dillon wrote on Twitter on Tuesday. "As a campaign, we're almost entirely powerless to stop misinformation. We can tweet corrections, but only a fragment of the people exposed will see it. This rests on Twitter, Facebook, and Google who let this go completely unchecked."

Dillon tweeted pictures of two tweets which went viral on Twitter claiming the shooter was an O'Rourke supporter. Oscar Villarreal, a spokesman for the Texas Department of Public Safety, told The Washington Post that there was no indication the shooter was an O'Rourke supporter.

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Shaffer retweeted a post from an account with the handle @suemo54 and the name "Sue Moore" which received thousands of retweets before it was suspended by Twitter. The tweet said that Odessa shooter Seth Ator was "a Democrat Socialist who had a Beto sticker on his truck." However, Ator didn't have a truck. He drove a gold Honda and hijacked a U.S. postal truck to carry out his attack.

Shaffer has also promoted baseless conspiracy theories about the attacks in Benghazi, Libya, in 2012.

Shaffer defended the tweet to the Post when told that it contained false information, saying, "That's not what I've seen from people."

Dillon noted that a Facebook post also containing the false information had 34,000 shares, and that on Google over the past week, the second highest trending search query was about whether O'Rourke had a connection to the shooter.

"The responsibility for stopping misinformation cannot be on the victims of misinformation attacks. It has to be on the tech companies who allow right wing operatives to spread misinformation. So I'm looking at you @Twitter @Google @facebook. What are you going to do about it?" Dillon wrote.

O'Rourke has called for stricter gun control in the wake of the mass shootings in El Paso, Texas, and Odessa last month. His campaign is also selling a new T-shirt on his campaign website that has a profane message condemning gun violence, repeating "This is f*cked up" six times and concluding with a call to action that reads, "End gun violence now."

The words echo O'Rourke's own response to the recent mass shooting in West Texas on Saturday.