Sgt. Shane Riddell, the lead investigator on Eichler's case, said "it would be negligent on our part if we didn't explore the possibility that he did have some involvement or may have some involvement" in Cruickshank's disappearance.
According to Regina police, Cruickshank was last seen on March 23, 2013 by a neighbour. They are treating this as a missing persons case.
Kristen Cruickshank, Kim's sister, said the 27-year-old woman was friends with Eichler and he would often call and try to spend time with her.
"The last few days before Kim went missing, Clay was messaging her. Clay was hounding her to hangout and at first she was just ignoring him."
She said the fact that Eichler has been charged with murder makes her sick to her stomach.
"I dont know, I want to be careful of what I say. We don't know anything for sure, but it doesn't look good," Kristen said.
Eichler facing two first degree murder charges
Eichler, 33, has been charged with the first degree murders of two aboriginal women and the violent sexual assault of another.
- Then on May 9, 2014, he was charged with killing 23-year-old Richelle Bear. She was last seen Aug. 24, 2013. Police also allege Eichler had sex with her dead body.
- And then on Dec. 18, 2014 he was charged with the aggravated sexual assault of yet another aboriginal woman. Eichler allegedly choked her with duct tape and a garden hose in 2012.
When Eichler was charged with the first degree murders police said if convicted, he would be the first serial killer in Regina's history.
Eichler has not been convicted of any murders and he hasn't been charged with any crime related to Kim's disappearance.
Eichler and Cruickshank were friends
Kristen said even though she lived in Ontario, she and her sister were very close and talked almost every day, sometimes several times a day.
And she said the subject of Eichler would often come up. Kristen said Kim was friends with him and occasionally took care of his young son.
Kristen said she was troubled by their friendship. She said she's known Eichler since he was 19-years-old and thought he was a bad influence on her sister, who was attempting to escape the drug scene and clean up her life.
"Kim was making some positive changes and [Eichler] would still text, call and for the most part she was ignoring him. But towards the end there she was feeling weak. It was hard for her to say no," Kristen said.
"He wasn't a healthy person for her at the time you know."
Court documents obtained by CBC show that when he was 18-years-old he went to drug rehab.
Then in 2004, Eichler was sentenced to jail time for possession of drugs for the purpose of trafficking.
And a court transcript reveals that in 2008 he was struggling with a crystal meth addiction.
Kristen said she knew Eichler had a drug problem and she believed he was trying to tempt Kim back into her old ways.
She said the two weren't in a romantic relationship, but she said Kim told her Eichler "had expressed wanting more than friendship from her. But she made it clear the feeling [was] not mutual."
Kim Cruickshank goes missing
Kim's mom Brenda will never forget the day her daughter went missing.
On the afternoon of Friday March 22, 2013, Brenda and Kim had a long and warm conversation on Skype.
"And she said I love you mommy. I'll talk to you later," Brenda recalled.
"We blew kisses and that's it. She was gone."
The next morning Kim didn't call Kristen as expected and she immediately felt something was wrong.
She contacted Kim's boyfriend and anyone else she could think of but no one knew where Kim was.
When police entered Kim's home they found her computers were gone and her dogs were locked in a room without food or water.
"Those dogs were attached at her hip. She doesn't leave those dogs. If they are not with her they are being babysat. Those dogs are not left alone," Kristen said.
"We knew something was wrong. Very wrong,"
Police arrest Eichler for murder
Then she said things took an even more troubling turn at the end of December 2013.
Kristen said she got a call from a Regina police officer.
"She just said 'head's up, we're making an arrest. It's not for your sister's [case]. It's for another girl.'"
Police told her they were arresting Eichler for the murder of Kelly Goforth.
"I literally just dropped to my knees and started crying."
Kristen's mother Brenda said she got a call too.
"They called me to let me know because they knew it was going to be in the paper and media, so they were giving us kind of a heads up on that development," Brenda said.
"[It] kind of hit me like a rock. I just sort of went numb — cried."
The women said police also called when the second murder charge was laid in May 2014 and when the aggravated sexual assault charge was laid the following December.
And they both said police have told them that they suspect Eichler played a role in Kim's death.
Police confirm that they phoned the women to update them on the status of the Eichler investigation.
And while they confirm they're investigating the possible connection between Eichler and Kim's disappearance, they won't call him a suspect.
Kristen said when she first learned that Eichler had been arrested for murder she immediately started to question whether or not he was involved in her sister's disappearance
"I want to believe that something crazy has happened and she's still [alive]. But I know with like every ounce of my being that she's not here anymore."
Kim's family losing hope
Kristen said she doesn't hear much from police these days. Neither does her mom.
Brenda said she has just about lost all hope that her daughter will ever be found alive. Now she just wants some sort of news.
"It certainly, I think, would make a huge difference in moving forward if we had a body to bury," Brenda said.
"But it doesn't look like that's going to happen. So that's a hard thing to live with - really hard."
Mother of murdered woman offers sympathies
The mother of Kelly Goforth said she knows the pain the Cruickshanks are going through.
Maxine Goforth's daughter was killed a year and a half ago and Eichler has been charged with her first degree murder.
"And I don't even know what events led up to her being murdered," said Goforth.
Goforth said the Cruickshanks have reached out to her family.
"They extended their hand to us. And we don't even know them. That woman must have a heart of gold," Goforth said.
"They have contacted us themselves to send condolences and they are praying. And every time there is a court date they contact my daughter and I really appreciate that because they're waiting too, I imagine."
And, like the Cruickshanks, Goforth is contacted by police when new charges are laid against Eichler.
She received a phone call in December 2014, shortly before police charged Eichler with aggravated sexual assault against an aboriginal woman in Regina.
"I cried and I cried that morning when they phoned me and told me," Goforth said.
Goforth says she was looking forward to the preliminary hearing, which was scheduled for later this month.
But it has now been postponed to the fall because Eichler doesn't currently have a lawyer.
Goforth says she is frustrated by the slow pace of the justice system but she has only praise for police.
"I cannot blame the police and I will not because I do know, they have been so good to us. I can't say [anything] bad about them and I will not. I realize they have to do their job and it takes time."
Goforth said she and all the other families are condemned to wait and hope for justice.
"There is nothing that will make it easier. Nothing. Just that common denominator with all moms that lost their babies," Goforth said.
"Same pain. Different circumstances. Still angry. You're always empty. I could never imagine losing my baby."