A Michigan dad on trial for the alleged role he played in his sons deadly mass shooting had his jail communication privileges limited because of threatening statements he made, authorities said.

James Crumbley, 47, is facing involuntary manslaughter charges for what prosecutors have argued was his gross negligence in allowing his son access to the gun used to kill four students and wound seven others at Oxford High School in 2021. The shooter, who was 15 at the time, received a life sentence last year.

Crumbley has now lost jail communication privileges after threatening statements he made while on the phone and in electronic messages, were found, the Oakland County Sheriffs Office said in a statement to HuffPost.

A court order signed by the judge overseeing Crumbleys trial denied him his communication privileges on Thursday, ruling he may only use a phone to speak to his lawyer. Crumbley will still be allowed to use an electronic tablet for research.

Authorities did not disclose details of Crumbleys alleged threats.

During the trial, jurors have been presented with text messages between Crumbley and his wife, Jennifer, about their sons deteriorating mental health and his access to a gun. The Crumbleys bought their son a semi-automatic handgun just days before the deadly shooting.

Jennifer Crumbley was found guilty of involuntary manslaughter charges in February, and is scheduled to be sentenced in April.