The Inland Valley Humane Society said the 8-week-old puppy was spotted by Lamar Walker on Monday in an alley behind his home in the 900 block of Loma Vista Street.
Walker heard the puppy whimpering and went to help, but when he went to pick him up, the dog yelped in pain.
"His fur was like, you know, black, you know what I mean, just burnt," Walker said. "It looked like he was in a lot of pain. I've never seen anything like that."
The puppy smelled of burnt fur, so Walker rushed the dog to the IVHS.
Shelter veterinarians said the Chihuahua mix suffered second-degree burns over much of his body.
The puppy, now named "Rocket," remains in critical condition and under 24-hour care from staff.
"All he knows is to love and to want to be loved and to crave attention from someone, and this is the attention they gave him unfortunately," James Edward with the IVHS said.
Walker said he can't get the image of Rocket's burned body out of his mind and hopes he can be the one to give him the home Rocket deserves.
"I feel like I'm attached to him," Walker said. "Nothing has ever touched me like that."
The IVHS said they are investigating the case as a deliberate act of animal cruelty and are offering a $5,000 reward for any information leading to the arrest and conviction of the suspect responsible.
Anyone with any information that can help investigators in this case is urged to call the IVHS at (909) 623-9777.
If you'd like to learn how you can donate and help Rocket, click here.