Two killings in Niagara Falls. N.Y., over the last three years are prompting serial killer speculation. Investigators are calling the killings "shocking to the conscience," according to CNN.

The two victims are Terri Lynn Bills and Loretta Jo Gates. The two were distant relatives and friends. Both suffered gruesome deaths, their arms, legs, and heads cut off and scattered, according to the New York Daily News.

Gates was killed in 2012. Bills was discovered in June. Both were dismembered, their bodies found in different locations than their bodies. These connections, among others, lead officials to think that the victims share the same killer.

"It's hard not to make that connection due to some of the similarities, most notably the condition of these ladies when they were discovered. They were also related through marriage. They shared some physical characteristics and led similar lifestyles," said Kelly Rizzo, Niagara Falls police captain, according to Time Warner Cable News.

Local law enforcement and FBI canvased the neighborhood on Tuesday. Authorities are actively looking for a suspect, asking for DNA samples and knocking on neighborhood doors, according to WKBW.

Bills torso was found in a vacant building, but her body parts have not yet been found, according to WKBW. Crews continue to canvas the area, giving out violations and looking into abandoned properties.

Officials continue to sort through evidence they've gathered, and have yet to make an arrest.