The girl's grandmother told the St. Paul Pioneer Press she had suspected Anthony A. Gomez since the head was delivered to her granddaughter, Crystal, in February in a box with candy hearts.
"I thought it was a sign that he loved her and she hurt him because she didn't want to be his friend anymore," Shirley Brown told the paper. "He knew that killing her dog was the thing that would hurt her worst of all; it would tear her heart out."
Gomez was charged with felony counts of animal cruelty and torture for allegedly beheading a dog.
"I think I can sleep a lot better now," said Crystal Brown. "It will make me feel way safer. Now we can walk around the whole block."
Crystal was devastated last month when Chevy, her 4-year-old Australian shepherd mix, disappeared. Two weeks later, a gift box addressed to Crystal was found at the front door of a house she shares with her grandmother. Inside, Crystal found Valentine's Day candy and a garbage bag containing her pet's head.
Police said Gomez lived a few blocks from Brown. He has a police record involving assault.
The case drew widespread media attention. The television show "America's Most Wanted" posted the case on its Web site, and donations pushed a $2,500 reward offered by the Humane Society of the United States to $20,000.
"Acts like this have disturbing implications for the community at large because there is a well-documented connection between animal cruelty and human violence," the Humane Society said on its Web site.