Days after the mysterious killing of a paddleboarder in Maine, state law enforcement officials said they are continuing to review leads and urged residents to remain vigilant.

“The Maine State Police recognizes the fear and discomfort that this incident has brought to the town of Union and the Crawford Pond community,” Maine State Police said in a statement Wednesday. “We remain steadfast in our efforts to investigate the death of 48-year-old Sunshine Stewart.”

Stewart was found dead July 3 in Union, roughly 30 miles east of Augusta, after authorities responded to a report of a missing paddleboarder, state police said.

An autopsy determined Stewart’s manner of death to be homicide, the agency said. Her cause of death has not been released. A state police official confirmed a report that Stewart was found “under unusual circumstances.”

The agency said the owners of a nearby campground have been cooperative with investigators and asked for information from anyone who saw Stewart paddleboarding between 6 p.m. and 9 p.m. July 2 near an island in Crawford Pond.

The agency has released few other details about her death, but said Wednesday that major crimes investigators have been examining all of the leads pushed through its tip line and continue to follow “every investigative and forensic avenue.”

A longtime friend of Stewart’s, Kimberly Hamill, told NBC News that it was “impossible” to make sense of her death.

“I grew up in Union, and as far I know, nothing like this has ever happened there,” she said. “For it to have happened to Sunshine is like, how could that even be? It just makes it feel like nothing will be right again ever.”

Hamill described Stewart as a solid friend who’d lived an incredible life: She was a carpenter who ran her own construction business. She was a boat captain who’d sailed to the Virgin Islands. She didn’t graduate high school but managed to earn a degree in marine biology, Hamill said.

“I want people to remember her as the force of nature that she was,” Hamill said. “She was such a loyal, good person. That was her most memorable quality — how much she believed in everybody.”