Vanessa Marcotte, 27, had gone out for a walk while visiting her mother in Massachusetts in August 2016 when she was murdered.
The person is only described as someone with knowledge of the park where Vanessa Marcotte was found dead.
Worcester County District Attorney Joe Early said the unknown person who killed Vanessa Marcotte received "scratches, scrapes and/or bruises."
Authorities asked for the public's help Tuesday as they struggled to find the killer or killers of a New York City woman whose body was found in woods near her mother's home in central Massachusetts after she went out for a jog and didn't return.
See photos of the investigation into the murder of a woman who worked at Google in New York City.
A homicide investigation has been opened in Princeton, Massachusetts, where the body of a 27-year-old woman was found after she went missing while out for a run during the middle of the day.
