An envelope that bore a postmark from Chattanooga and containing a photo of a dog strung between two trees arrived at PETA's office in Virginia Tuesday.
Enclosed in the envelope was what is believed to be the severed ear of a dog in the gruesome photo.
PETA members are offering a reward of $5,000 and the Humane Educational Society of Chattanooga has added another $1,000 for information leading to the arrest and conviction of those responsible.
It shows what appears to be a light reddish-brown, pitt bull mix that's around 2 to 3 years old tied between two trees.
"The picture is graphic, but we do hope people will look at it in an attempt to possibly recognize where the dog came from, maybe the location of where the dog is pictured at, or possibly who owns the dog," Bob Citrullo, Executive Director for the Humane Educational Society of Chattanooga.
Citrullo said he believes someone is trying to send a message to PETA.
"This is a horrific way to do something like this. Again, we're free to express our thoughts, but not like this, of course," Citrullo said.
Right now, Citrullo said authorities are looking at fingerprints to see if that'll connect them to the person or people who did this.
PETA is calling it a torture killing.
"It should send chills down anyone's spine to imagine someone out there hanging, killing, and cutting body parts from a dog who could only have been terrified—and then bragging about it to an animal-protection charity," says PETA Vice President Colleen O'Brien.
"The whole community is at risk if a violent person who acts out in this way is not found and held responsible, and PETA urges anyone with information about this case to come forward."
Citrullo worries this type of behavior could lead to something else.
"That's why it's so important to try and find the people responsible for this. To prevent this not only from this type of thing happening, but again from preventing it from progressively getting much worse to where they go and become serial killers and of course, they'll go after people," Citrullo said.
It's unclear if the person who sent the envelope is from Chattanooga.
Anyone with information about this case is encouraged to call PETA at 757-962-8328 or HES at 423-624-5302.