A 57-year-old Tampa woman has been charged with threatening to kill the parent of a victim of the Sandy Hook Elementary School massacre because she believes that the shootings never happened, officials said.

Lucy Richards is accused of sending several threatening text messages to the child's parent, saying, "You gonna die, death is coming to you real soon," a federal indictment said.

The Sandy Hook massacre in Newtown, Connecticut, on Dec. 14, 2012, was one of the worst mass shootings in U.S. history, resulting in the deaths of 20 children and six adults.

"Richards' belief that the school shooting was a hoax and never happened motivated her to make the charged threats," a statement from the U.S. Attorney's Office said.

The threatening text messages were allegedly all sent on Jan. 10, court documents said.

Richards was arrested Monday and charged with four counts of transmitting threats in interstate commerce.

If convicted, she faces up to 20 years in prison.