DALLAS -- Mercy, the 10-month-old puppy who was doused with gasoline and set on fire, died Sunday at about 9:30 p.m. at the veterinary clinic where she was being treated.

Doctors said Mercy showed some improvement Saturday, but her condition started to deteriorate Sunday afternoon. She was given a plasma transfusion, but shortly afterward her heart -- weakened by burns over 60 percent of her body -- stopped beating.

The young pit-bull mix was rescued Friday, April 14, by a Dallas man who saw her in the wooded area behind the Rock Creek Apartments at Preston and Belt Line in Far North Dallas. He took the dog to Operation Kindness Animal Shelter in Carrolton, where she was given immediate veterinary care.

Mercy was transferred to the Dallas Veterinary Surgical Center last Monday. She had surgery the following day to remove most of her burned ears and begin the painful debridement treatment. Doctors cautioned that, because of the severity and extent of her injuries -- which also included stab wounds and cuts -- her prognosis was guarded.

"All of us at Operation Kindness, as well as thousands of people who have been moved by her plight, are grieving for Mercy," said Jonnie England, executive director at Operation Kindness. "We were so hopeful that this beautiful, gentle dog, who had suffered and endured unbearable pain, would pull through in the end. It's more important than ever that the person who brutalized her be caught and brought to justice, for Mercy's sake."

The reward now stands at $10,000 for information leading to the arrest and conviction of the person responsible for torturing and, ultimately, killing Mercy.

The case is being investigated by Dallas Animal Services' Cruelty Division and the Dallas Police Department. Anyone with information should call 311 or Dallas Animal Services at (214) 671-0246.