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MIAMI (CBSMiami/AP) — Three pit bulls that attacked another dog in Gainesville have been euthanized.

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Alachua County Commissioner Robert Hutchinson tells the Gainesville Sun that the dogs belonging to Nathaniel Petttiford often had to be tranquilized while in the county’s care because they were so aggressive.

The dogs were declared dangerous and held by the county after attacking Linda Swinburn and her dog Bella while they were walking on Sept. 22.

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Authorities said Swinburn tried to fend off the dogs and was injured. Bella died a short time later.

Petttiford was given 30 days to appeal the dangerous dog ruling or reclaim the dogs, which would have required taking out a $500,000 insurance policy for each one, sterilizing and microchipping them and posting a “dangerous dog” sign. He did neither.

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(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)