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SACRAMENTO-

Stephanie Douglas appears shaken up. It’s been almost a week since her sister, Sarah, was stabbed and strangled to death.

Sacramento County Sheriff’s detectives say the prime suspect is Sarah’s fiancé, Cal Fire Battalion Chief Orville Fleming.

“The last phone call,” Douglas said. “The last scream. You know, I can’t even sleep at night.”

The final moments of her sister’s life, captured in a phone call that Stephanie Douglas will never forget.

“He pushed her down. She was fighting so hard,” she said.

Douglas described to FOX40 a scene that was beyond gruesome.

“That’s some serial killer (expletive),” Douglas said. “He couldn’t control her; he threw a sheet over her, so she couldn’t fight anymore. He pushed her down and tied it around her neck.”

Investigators say Sarah Douglas was stabbed more than 20 times with a 9-inch blade and strangled.

“That’s a monster. You stabbed someone over 20 times and you sat on her back and strangled her,” she said.

Douglas says her family has to make special arrangements to lay their loved one to rest.

“Her scalp, her neck, her chest. She has to wear a turtle neck and long sleeves.”

In the search for Fleming, investigators warn the public he’s likely armed and dangerous, known to have .45 and .25 caliber pistols.

Family admits Sarah Douglas met her 55-year-old fiancé on the popular escort website, MyRedBook.

Douglas says before her death, Sarah tried to get her information removed.

“It’s not what you’ve done in your past that matters; it’s what you do now that counts,” she told FOX40.

Investigators say they have been made aware of a possible sex tape between Sarah Douglas and firefighters at the Cal Fire training station in Ione, something Stephanie Douglas says is an insult to her sister’s character.

“The sex tape is irrelevant,” Douglas said. “That’s irrelevant to the fact that my sister was murdered.”

UPDATE: Cal Fire Suspect Known to Change Appearance, Carry Guns and Cal Fire Gate Keys

DETAILS: Investigators Reveal Suspect’s Past with Escorts, Sex Tape at Cal Fire Station

WATCH: Friends and Family Gather to Remember Sarah Douglas, Cal Fire Battalion Chief Still Missing

READ: Cal Fire Battalion Chief Suspected in Homicide, Victim’s Family Describe his Demeanor