Christian Slater's Father Threatened to Kill Him and His Mother, She Alleges in New Legal Documents
04/19/2016 AT 06:10 PM EDT
In legal documents obtained by PEOPLE, Christian's mother Mary Jo Slater issued a declaration in support of her son's motion to strike the lawsuit, detailing claims of her ex-husband Thomas Knight Slater's diagnosis with manic-depressive schizophrenia and threw her into traffic when she was five months pregnant with Christian. (Thomas, 80, is suing his son for at least $20 million, claiming he "ruined" Thomas' acting career because the Mr. Robot star said his father was "suffering from manic-depressive schizophrenia" in a December 2015 interview – years after Thomas' last credited role on IMDb, a small part in the 1988 action film Midnight Run.)
In the documents, Mary Jo, 70, claims Thomas was taken to the hospital sometime around the year 1972 after threatening to kill her and Christian, who was 3 years old at the time. According to the papers Thomas was diagnosed as "a paranoid schizophrenic" and was kept in a straitjacket when she would visit him at the hospital. Mary Jo claims Christian was made aware of his father's diagnosis.
In the motion, Mary Jo also claims her ex-husband threatened to kill the producer and the director on a soap opera he was starring on when Mary Jo was five months pregnant with Christian. According to Mary Jo, she attempted to stop him from doing so, at which point he threw her down in the middle of a busy street in New York City before oncoming traffic. Mary Jo claims Christian was also later made aware of his father's actions.
Thomas denies his ex-wife's claims that he acted violently or threatened violence, and also denies that he has suffered from mental illness.
"She's a tremendous exaggerator and a liar beyond belief. She has defamed me and denigrated my reputation over the last 30 years," Thomas tells PEOPLE.
In her declaration, Mary Jo, who is a casting director, also claims Thomas has blamed her for his lack of work since 1988 and sued her unsuccessfully over the matter in 1998.
The motion also includes copies of a letter Thomas reportedly sent her in 2008, in which he accuses her repeatedly of "blacklisting" him from the industry.
At the time the original lawsuit was filed in February, a family source told PEOPLE Christian's father has a long history of personal struggle.
"Christian has done what he can for him financially by supporting him for many years, but eventually had to distance himself because of his erratic behavior," said the source.
Thomas previously claimed in a December 2015 National Enquirer interview that Mary Jo had "poisoned" his son against him.
"It's been a long and difficult situation," said the source. "The lawsuit is baseless."
Meanwhile, a source close to Christian, now 46, tells PEOPLE the actor "has been battling this privately for many, many years."