A paddleboarder was mysteriously murdered in a small Maine town — and authorities are urging calm as the killer remains unknown.

Sunshine Stewart’s body was found under “unusual circumstances” on an island on Crawford Pond in the community of Union around 1 a.m. July 3, after she never returned from her solo paddleboard outing the night before, Maine State Police told NBC News.

The island, known as 100 Acre Island, sits in the middle of the massive pond and is only accessible by boat, police said, WMTW reported.

Officials determined the 48-year-old’s death was a homicide — however no cause has been revealed and no suspects have been identified more than a week later as a manhunt for the murderer is underway.

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

“We understand the community’s concerns and ask that residents continue to remain vigilant, be aware of their surroundings, and report any suspicious activity to law enforcement,” police said.

Stewart, an experienced paddleboarder and outdoor adventurist, went out on Crawford Pond by herself at about 6 p.m. on Wednesday, July 2 near the Mic Mac Campground.

When she did not return six hours later, she was reported missing, police said.

Stewart was located on the island by a game warden after a mult-agency search.

Police said they’ve been working with the owners of the Mic Mac campground, who have been cooperative and assisting with the investigation.

The campground said in a Facebook post that investigators have been using the campground to access the crime scene, which is not part of the camp property.

Investigators have been following up on several tips received through their hotline and have asked for any witnesses who may have seen Stewart paddleboarding on July 2 between 6 and 9 pm on Crawford Pond to contact them.

“Detectives from Major Crimes Unit Central have been reviewing all of the leads pushed through our tip line and continue to follow every investigative and forensic avenue,” state police said.

Stewart, from Tenants Harbor about 25 miles from where she was found, was a contractor who previously worked as a marine biologist, lobster catcher and boat captain and even once sailed all the way to the Caribbean, according to her sister, Kim Ware.

“Captain Sunny was an amazing person” who “would give you the shirt off her back. The strongest person I know!” she said in a statement to WMTW.

“Sunny loved the outdoors, hiking, boating, paddle boarding, and yoga. To know Sunny is an amazing blessing! My sister and my best friend. The aunt that stepped up to help me raise her nephews. She has so many that call her family. Truly an amazing woman. Now we have to rally and give her justice!” said Ware.

Union, a town of about 2,500 people, is located about 30 miles east of the Maine state capital Augusta.