Moments before opening fire into a Pittsburgh synagogue, police say suspected shooter Robert Bowers posted his last anti-Semitic message on Gab.

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“Gab did not kill anybody,” said Andrew Torba, Gab's CEO.

He defended the social network to conspiracy theorist Alex Jones of the far-right site Infowars.

“Social media posts never killed anybody,” Torba added. “The only people responsible here is the individual.”

KIRO-TV in Seattle sat down with University of Washington assistant professor Kate Starbird, who studies online conspiracies and misinformation, and asked her what responsibility social media bears in real life events.

“I think there's the responsibility, the question is actually difficult because I don’t think we can assign responsibility to one thing. There's a lot of different factors that are converging at one time,” Starbird said.

Starbird did not want to discuss Gab specifically but did say some people are purposefully using social media as a radicalization tool.

“We are seeing social media act as one channel of radicalization,” Starbird said. “Five years ago, we were talking about ISIS; now we are talking about white supremacy, ethno-nationalism and other kinds of things.”

KIRO asked if social media companies need to do a better job monitoring the content on their sites and referring questionable content to authorities before it escalates to disaster or violence.

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“That’s a hard question. I don’t know if I am capable of answering it. Social media is faced with two hard questions, just to decide what’s toxic and what’s not,” Starbird said.

Starbird also says there are questions of how to monitor the content.

“Maybe they should, but it’s not an easy problem to solve,” Starbird said.

KIRO also learned that Gab was previously hosted by Microsoft Azure, which threatened to cut ties with the site after anti-Semitic posts over the summer. Microsoft declined an interview. A spokesperson would only say Microsoft terminated its Azure agreement with Gab last month.