The FBI has joined the manhunt for a killer who brutally stabbed to death a woman and her dog in an Atlanta park last week, while the woman’s friends claim some city surveillance cameras weren’t working the night of the murder as unanswered questions continue to swirl around the investigation.

ATLANTA POLICE ID WOMAN, DOG STABBED TO DEATH IN PARK; MANHUNT CONTINUES FOR SUSPECT IN ‘GRUESOME’ MURDER

FBI spokesperson Kevin Rowson confirmed Thursday that agents were assisting Atlanta police in the murder probe of 40-year-old Katherine Janness and her dog Bowie, who were both discovered dead inside Piedmont Park in the city’s Midtown neighborhood early Wednesday. No arrests have been made as of Monday.

Police have described the scene of the stabbing as "gruesome," but little other information has been released as investigators continue searching for clues.

Janness, 40, and her dog Bowie were identified as the victims of a brutal stabbing Wednesday in midtown Atlanta's Piedmont Park on Wednesday night.

Janness, 40, and her dog Bowie were identified as the victims of a brutal stabbing Wednesday in midtown Atlanta's Piedmont Park on Wednesday night. (Atlanta Police Department)

Investigators have gone door-to-door asking neighbors for surveillance footage, The Atlanta Journal-Constitution reported. The aim is to help them retrace Janness’ steps and glean any clues they can from the video.

But Janness’ friends on Friday told the paper that some of the city’s surveillance cameras in the area, including one facing the park entrance, weren’t working at the time of the killing.

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"If it had been working, it would have shown something," Heather Johnson said.

Police have not said whether any of the park’s cameras malfunctioned the night of the killing, telling the paper that investigators were reviewing footage from the area.

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Investigators on Wednesday released an image taken from a security camera showing Janness with Bowie shortly before the killings. No names or images of a potential suspect or person of interest have been released as of Monday. 

Atlanta police Deputy Chief Charles Hampton has said it’s too early to determine a motive for the killing.

Investigators are offering a $10,000 reward for information regarding the murder.

The Associated Press contributed to this report.