John Grace, 50, is accused of sending a message on Monday, Dec. 12, that made specific threats, CBS reported, though police did not release what he said or why he was angry.
Concord police secured Hunter's office and placed a cruiser outside her home. Officers arrested Grace, searched his home, and seized his firearms, the news station reported.
Grace is being held under house arrest and is required to wear a GPS monitoring bracelet, NBC Boston reported. Authorities did not release his charges.
Concord police Chief Joseph O'Connor sent a message to parents and school staffers to allay their fears about Hunter's safety.
"This note is limited to ensure a successful prosecution." O'Connor wrote in his message obtained by WCVB. " Please know that the police department works very closely with the schools to ensure the safety of all. I am sure you can all appreciate this has been a difficult few days for Dr. Hunter. Please join me in keeping her in your thoughts."
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