The piece of life-saving equipment was snatched from the Glenard Road in Newtownards last night (Sunday).
According to police, the defibrillator was recovered a short distance away but it had been damaged during the theft.
A PSNI spokesperson said: "Not only are these costly but this particular one will be out of use for some time whilst it’s investigated and checked to make sure it’s still working correctly."
Anyone who has any information about the theft - which occurred around 10.30pm - is urged to call police on 101, quoting serial 1587 5/5/19.
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Members of the public have reacted angrily to news of the theft, describing it on social media as "sickening" and "despicable".
One woman said: "My dad has passed away this week from a heart attack, A defibrillator can save a life, these stupid people need educated."
Another added: "I wonder how they'd feel if their mother, father, brother, sister or grandparents needed this and it wasn't there. They have taken away someone's last chance."