— -- The families of the victims of the 2015 San Bernardino, California, mass shooting filed a federal lawsuit Wednesday against Twitter, Facebook and Google, accusing the companies of knowingly supporting ISIS.
According to the lawsuit, filed in federal court in Los Angeles on behalf of their attorneys, the families of Sierra Clayborn, Tin Nguyen and Nicholas Thalasinos, all of whom were killed in the terror attack, claim the two social media platforms and one search engine provide the terrorist group with support and a platform to grow.
"For years, Defendants have knowingly and recklessly provided the terrorist group ISIS with accounts to use its social networks as a tool for spreading extremist propaganda, raising funds, and attracting new recruits," the families said in the lawsuit. "Defendants are information content providers because they create unique content by combining ISIS postings with advertisements in a way that is specifically targeted at the viewer."
On Dec. 2, 2015, 14 people were killed at Inland Regional Center when heavily armed gunmen who were "on a mission" opened fire at the center, a facility that provides services to people with developmental disabilities.
The perpetrators, Syed Rizwan Farook, 28, and his wife, Tashfeen Malik, 27, died in a shootout with police hours after the attack. Sources told ABC News at the time that Malik, who used an alias on social media, allegedly pledged her allegiance to Abu Bakr al-Baghdadi, the leader of ISIS, ahead of the shooting spree.
In their lawsuit against the social media sites, the families of the San Bernardino victims say that Facebook, Twitter and Google have acted as a supporting tool for ISIS to "attract new recruits and inspire lone actor attacks."
The families highlight an ISIS recruitment video that was posted on social media in June 2014. While YouTube removed the video, the lawsuit points out that a Twitter link remained available for download and was promoted through re-tweets by ISIS-related accounts.
In addition to a recruitment video, a Twitter page was made for Al-Furqan, ISIS's media wing responsible for producing multimedia propaganda. The lawsuit noted that Al-Furqan's Twitter followers "have grown at an astonishing rate," and says Al-Furqan has used the platform to post "messages from ISIS leadership as well as videos and images of beheadings and other brutal forms of executions."
As of December 2014, ISIS has had an estimated 70,000 Twitter accounts and posted at least 90 tweets every minute, according to the lawsuit. The families also claim that the terrorist group has used Google and Facebook in a similar manner and says that the advertising revenue Google earns is shared with ISIS.
In response to the lawsuit, Facebook told ABC News in a statement, "We are committed to providing a service where people feel safe when using Facebook. There is no place on Facebook for groups that engage in terrorist activity or for content that expresses support for such activity, and we take swift action to remove this content when it’s reported to us. We sympathize with the victims and their families."
Twitter responded to the lawsuit by directing ABC News to a statement on its Twitter Rules page which states that the platform clearly prohibits threats of violence or the promotion of terrorism, and pointed to data in their latest Transparency Report that reveals from July 1, 2016, to Dec. 31, 2016, a total of 376,890 accounts were suspended for violations related to promotion of terrorism.
Twitter also referenced a similar lawsuit they won in 2016 that linked them to providing support to ISIS.
Google did not respond to ABC News request for a statement, but according to YouTube's website, the platform "strictly prohibits content intended to recruit for terrorist organizations, incite violence, celebrate terrorist attacks or otherwise promote acts of terrorism."
ABC News' Alex Stone and Julie Sone contributed to this report.