The site gained scrutiny when one of its users allegedly killed 11 people at Pittsburgh’s Tree of Life synagogue in 2018. The Pittsburgh Post Gazette wrote that “Network Contagion Research Institute director Joel Finkelstein said there was little or no pushback from others on Gab.com when [the alleged shooter] posted or shared anti-Semitic and anti-immigrant slogans and memes. There was plenty of encouragement.” Before the attack, the alleged shooter wrote on Gab: ““HIAS [the Hebrew Immigrant Aid Society] likes to bring invaders in that kill our people. I can't sit by and watch my people get slaughtered. Screw your optics. I'm going in."

The site also sponsors white nationalist and anti-semitic organizations, including Holocaust denier Nick Fuentes’ America First Political Action Conference and the virulently racist website VDare.

Media Matters contacted Gab CEO Andrew Torba for clarification about what exactly Mastriano paid his company to do. He replied: “Do you accept Jesus Christ as your Lord, Savior, and King? Otherwise I don’t speak to reporters who are not Christian.”

Torba has a history of pushing anti-semitism and white nationalism and lauded the January 6 insurrection.

Mastriano has embraced Gab -- he has an account on the platform and was interviewed by Torba on May 2. The two praised each other during that talk, with Mastriano telling the Gab CEO: “Thank God for what you’ve done.” Gab endorsed Mastriano on May 12, with Torba writing: “Finally we have a strong Christian man to lead PA out of the pit of hell and into the glory of God.”

Several Republicans have advertised on Gab, including Rep. Marjorie Taylor Greene (R-GA), Rep. Paul Gosar (R-AZ), and Georgia GOP Senate nominee Herschel Walker.