Schoolgirl April Millsap, 14, texted her boyfriend just before her death according to Michigan Poilce, who are looking for a person of interest. Courtesy: myFOXdetroit.com

THE family of a teenager murdered while walking her dog on a nature trail believe she may have known her killer.

Police said Michigan schoolgirl April Millsap, 14, texted her boyfriend “OMG ... I think I’m being kidnapped” to her boyfriend just before her death.

A couple walking the well-known Macomb Nature Trail in Armada, just north of Detroit, found April’s body last Thursday night. Her dog Penny was standing guard.

It later emerged the dog had repeatedly approached other hikers before successfully leading the couple to her body.

April’s grandfather Dennis Levans told the Detroit Free Press the family suspected her killer was no stranger.

“That’s what we think,” Mr Levans said.

“It’s almost like it had to be something like somebody knew them. We can’t think of any other reason. We can’t come up with any other logical reason. We’re at a loss, she was just a beautiful young lady.”

Police said that when April sent that disturbing text message: “OMG ... I think I’m being kidnapped”, her boyfriend and her mother set out in their cars to find her.

Mr Levans said the boyfriend, who has been ruled out as suspect by police, did not realise April was being serious.

“Sometimes kids can be silly,” Mr Levans said. “He might have thought of it as being a prank or something. Why wouldn’t he have called the police right away?”

At the weekend, about 300 people attended a vigil for April outside St. Mary Mystical Rose Church in Armada.

Police are looking for two vehicles which may be connected to April’s death including a grey, “beat-up”, painter’s-type van and a small blue-and-white motorcycle. A sketch of a person of interest has also been circulated.