The mother of a man who carried out the terrorist massacre that claimed 14 lives during a Christmas party at a county building in San Bernardino in 2015 has agreed to plead guilty to a federal charge of destruction of evidence for shredding a map her son had created in connection with the attack, authorities said Tuesday.

Rafia Sultana Shareef, also known as Rafia Farook, 66, of Redlands, reached a plea deal with prosecutors on Monday, and the documents became public Tuesday, according to the U.S. Department of Justice. She has agreed to admit to a federal charge of alteration, destruction and mutiliation of records.

Her son, Syed Rizwan Farook and his wife, Tashfeen Malik, killed 14 people and wounded 22 more when they opened fire at the Inland Regional Center in San Bernardino on Dec. 2, 2015. Syed Farook was a county employee and the attack targeted a Christmas party attended by his coworkers.

The attackers were subsequently killed in a shootout with police that also wounded an officer.

Shareef lived with her son and his wife at a home in Redlands at the time of the attack, prosecutors said.

In the hours following the massacre and shootout with police, Shareef learned that her son had been identified by law enforcement officials as a suspect in the attack, DOJ spokesman Ciaran McEvoy said in a written statement.

“In the presence of family members that afternoon, Shareef expressed her belief that her son and daughter-in-law had perpetrated the IRC attack,” McEvoy said.

“Prior to leaving the family home with her infant grandchild at 3:41 p.m., Shareef went into her son’s bedroom, grabbed at least one document that appeared to be a map, and fed it into a shredder, according to the plea agreement. Shareef admitted that she knew her son had produced the document, and she believed it was directly related to his planning of the IRC attack,” according to McEvoy.

The charge that Shareef agreed to plead guilty to carried a maximum penalty of 20 years in federal prison. But the plea agreement reached with prosecutors references a prison term of 18 months.

Shareef is scheduled to make her initial appearance in federal court in Riverside on March 16.