Suzanne Simpson's Sister Recounts Terrifying Hours When She Realized Something Bad Had Happened: 'I Knew' (Exclusive)

Suzanne Clark Simpson’s sister had a bad feeling when she first learned the Texas mother of four was missing.

“It’s inconceivable,” Teresa Clark tells PEOPLE. “I knew she wasn’t alive. Suzanne doesn’t go missing.”

Suzanne, a San Antonio realtor, was last seen when she, her husband and their youngest child attended a birthday party on Oct. 6.

At the time, Clark was at a hotel in Hong Kong when she received a message from one of Suzanne’s college-age children asking Clark if she’d spoken to her sister. No one had heard from Suzanne in 16 hours.

“I knew immediately that my sister was gone,” Clark says.

Then she learned her sister had missed a hair appointment.

“The big first red flag was when she missed her hair appointment — nobody misses a hair appointment,” Clark says.

Then her sister didn’t pick up her youngest child from kindergarten.

“That was the second red flag that there was nothing normal about this,” Clark says.

Suzanne was officially reported missing on Oct. 7. After her disappearance, her husband of 22 years, Brad Chandler Simpson, was charged with assault causing bodily injury to a family member and unlawful restraint.

Want to keep up with the latest crime coverage? Sign up for PEOPLE‘s free True Crime newsletter for breaking crime news, ongoing trial coverage and details of intriguing unsolved cases.

During an Oct. 9 press conference streamed by KENS, Olmos Park police chief Fidel Villegas said Brad was arrested after he failed to show up to a meeting with police. Villegas claimed that after learning about Suzanne’s disappearance, police learned about an altercation at the family’s home that had possibly turned physical.

On Monday, Nov. 4, Brad’s defense attorney, Steven Gilmore, told PEOPLE, “I have no additional comments at this time.”

On Thursday, Nov. 7, Brad was charged with murder, according to the Texas Department of Public Safety. The Olmos Park Police Department will be holding a press conference at 2 p.m. Friday, Nov. 8.

Gilmore did not respond to PEOPLE’s request after the new charges.

Clark tells PEOPLE that to her knowledge, her sister’s body has not been found yet — but she believes her sister is no longer alive: “There’s no hope,” she says.

Still, authorities continue to search.

“They will find her,” Clark says. “She was a great mom, and a great daughter, and a great wife. She was beloved. We’re going to do everything we can to bring her home.”

If you are experiencing domestic violence, call the National Domestic Violence Hotline at 1-800-799-7233, or go to thehotline.org. All calls are toll-free and confidential. The hotline is available 24/7 in more than 170 languages.