(NewsNation) — On April 8, the body of 32-year-old Joanna Speaks was found in a rural area near Portland, Oregon.

A total of six women have been found dead within 100 miles of Portland in recent months, but the Speaks case is the only one that has been officially ruled a homicide at this time.

A medical examiner said Speaks showed signs of blunt-force trauma to the head and neck.

Robyn Speaks, the sister of Joanna, told NewsNation’s “Banfield” on Monday that authorities have been “very helpful” with her sister’s case.

“I think that they (police) are trying to make sure that they keep the public from being too freaked out about (a) serial killer. Either way, women are dying. And the numbers are rising,” Robyn said on “Banfield.”

Robyn said that that her sister was “fun and excited about life,” but in recent years had struggled with addiction and homelessness.

There’s a lot of fear and speculation as to who could be behind the six deaths, but Portland police are trying to shut down mounting anxiety. At this point, police say they have not found any sort of connection between the six deaths.

“Victimology is huge. It sounds like some of these victims were in a vulnerable population. And right now, in my experience, … that population is where the predators are going because they are trying to find the victims in order to be able to satisfy their own needs,” Paul Holes, the investigator whose work led to the Golden State Killer’s identification and arrest, said during an appearance on “Banfield.”

In order to coin the killer as a “serial killer,” Holes said law enforcement needs to find something that connects the killings.

Holes said that in his experience, law enforcement is typically “ill-prepared” for serial killer cases.

“Oftentimes, even very experienced homicide investigators have never worked that type of case. There are some subtleties that the offender may be leaving behind across multiple cases that are being missed,” Holes said.