QUINCY (CBS) — A vigil was held Saturday for a pit bull-mix puppy that was euthanized after it was found malnourished, stabbed and burned in a Quincy playground.

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The details of the torment that the dog now known as “Puppy Doe” endured spurred hundreds of people to attend Saturday’s demonstration outside Quincy City Hall.

“I need to be at this candle vigil to let Puppy Doe know how sorry I am that we humans let her down and that we failed to protect her,” said Diane Holler O’Meara.

The pit bull-mix was found badly injured on Aug. 31.

Mary Nee, president of the Animal League of Boston, said the treatment of the dog is among the worst cases of animal abuse the group has ever seen.

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“I have spoken to many veteran staff and volunteers at the League about Puppy Doe. Never in our collective memory do people remember a case so horrific. … We are all shaken to the core by the details of what happened to this poor dog.”

Saturday’s candlelight vigil called for justice, and Norfolk County District Attorney Michael Morrissey vowed his office is seeking it.

“We’re here because this kind of cruelty diminishes us as a society and diminishes us as a community,” Morrissey told the crowd. “It is highly unlikely that this level of sadistic cruelty, which I have referred to as torture, can be shown to one living creature and not to others.”

The DA cited studies that show high numbers of animal cruelty offenders go on to commit more violent crimes, including murder.

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A fund-raiser has been started to help further the investigation. The Animal Rescue League of Boston is offering a $5,000 reward for information leading to the arrest of anyone responsible for Puppy Doe’s abuse. Misty’s Journey and Second Chance Rescue in New York City has added an additional $10,000 in reward money. Additional rewards have been offered as well, some as high as $2,000, from other animal rights organizations.