DENVER -- The owner of a missing dog in Evans, Colo., said he has received a ransom note that threatens to kill his pet if he doesn't pay $100.

The note came in a bag of dog excrement, said Kelley Borland.

His Jack Russell terrier was discovered missing from his fenced back yard on Sept. 10.

Borland contacted the police, and Humane Society of Weld County, in an effort to find his dog, Jack. He also ran a classified advertisement in the Greeley Tribune newspaper.

When he came home from work Tuesday, he found a plastic bag in front of his house with the note and the dog droppings.

The note said, "Your dog is alive. If you want to keep it that way, put $100 dollars in a yellow envelope and leave it at the skate park behind the ramp that faces east. No later than 10 p.m. on 9/20."

Borland said he didn't have $100 but left a note asking the writer not to kill his dog.

He told the Tribune that the dog excrement looked like it came from his back yard.

"It looked like my dog's poop," Borland told the newspaper, "but I'm not a dog poop analyst."

Police said they believe the note was written by a juvenile because there's a 10 p.m. juvenile curfew at the skate park. They also believe the person who wrote the note doesn't have the dog, but probably saw the newspaper ad.