Some conspiracy theorists say the Sandy Hook mass shooting never happened. Now, after years of harassment, families of the victims are fighting back.

A paranoid conspiracy theory has acquired a new and disturbing power in America, and it has been spread by an alternative media outfit that has been linked to President Trump.

Twenty-six people, mostly young children, died at Sandy Hook Elementary School in 2012. They were the victims of a man named Adam Lanza, who killed himself after the slaughter. It was a shocking tragedy, even in a country used to regular gun violence.

Soon false rumours began to circulate online, that the attacks were staged using actors. Although they had no basis in truth, hundreds of YouTube videos, blogs, and tweets repeated the conspiracy theories. And the rumours were pushed by an alternative media mogul named Alex Jones. His online news site Infowars has millions of listeners and viewers. He's interviewed President Trump, who has repeated Infowars stories on his own Twitter feed and in speeches.

Lenny Pozner's son Noah was killed at Sandy Hook. And, as it happens, Lenny Pozner was also a fan of Infowars. That's how he first found out that people were saying the mass shooting was entirely staged.

As the "hoaxers" went to greater extremes to spread their fake news - even targeting grieving parents - Lenny Pozner led the online fightback. With the help of the Sandy Hook community, he tried to turn the tables on the conspiracy theorists.

Presenter: Mike Wendling.

Producer: Sam Judah.