Judy Shepard says she's "terrified" of a Donald Trump presidency in a new ad denouncing the Republican presidential nominee's politics of hate.

Judy is the mother of Matthew Shepard, the gay University of Wyoming student who was brutally murdered in 1998 by two homophobic men he befriended in a Wyoming bar.

Judy's activism in the wake of her son's death was chronicled in the 2013 documentary Matt Shepard Is a Friend of Mine, and was essential in passing the federal Hate Crimes Prevention Act, which protects LGBT people from crimes based on their sexual orientation.

"When I see the hate that Donald Trump brings to his campaign for president, it terrifies me," Judy says in the new ad, amid a montage of Trump's many violent calls-to-action.

"Words have an influence. Violence causes pain. Hate can rip us apart. I know what can happen as the result of hate, and Donald Trump should never be our president."

Check out the powerful new ad, which was produced by pro-Clinton PAC Priorities USA, below: