In November 2007, after 20 years of marriage, 57-year-old Mary Koontz was forced out of the home she shared with her husband, Ronald Koontz.
She moved into a condo where she felt isolated and rejected. The Baltimore country teacher would call her estranged husband and her teenage daughter daily, leaving unhinged messages on their voicemails.
On June 19th, 2009, Mary used a secret key to sneak into the home she once shared with her husband. She ambushed and shot the 66-year-old school administrator four times and killed him.
She also tried to kill her 16-year-old daughter Kelsey, but the teen was unharmed and survived.
Police arrested Mary the same day. She took the stand at trial and tried to claim insanity, but the jury rejected her argument and convicted her of first-degree murder, attempted murder, and two weapons charges on July 8, 2010.
on August 10, 2010.She received two life sentences plus two 20-year sentences.
DOB:
November 1949Conviction(s):
- First-degree murder
- Attempted first-degree murder
Date of crime:
June 19th, 2009Location(s):
Glen Arm, MDDate of arrest:
Same DayDetails:
Killed her estranged husband and tried to kill her 16 year old daughter.Confirmed Victim(s):
- Ronald Koontz (67)
- "Kelsey" Koontz(16) Survived
Method:
ShootingMotive(s):
RevengeSentence:
Life without parole (x2) plus 20 years (x2)Current whereabouts:
Maryland Correctional Institution for Women in Jessup, MDLast Updated on 03/18/2026
