The parents of a missing Missouri mother are standing by claims that her husband had involvement in her disappearance.
Jacque Sue Waller, a 39-year-old mother of young triplets, was reported missing June 1 shortly after visiting with her estranged husband, James "Clay" Waller, at his home in Jackson, Mo.
In an interview on ABC's Good Morning America, Ruby Rawson, the mother of Waller, said she confronted her son-in-law James and asked him what he did to Jacque.
"He said 'I didn't do anything," Rawson said, in which she replied, "yeah, you did and you know you did, because of all the threats you've been saying to her over the last year."
Stan Rawson, the father of Waller, also wrote a message to James on a 'Find Jacque S Waller' Facebook page, the Daily Mail reports.
"You will regret hurting my girl and the Tripps -- I promise you will!"
A statement released by James Waller's attorney, read "Mr. Waller misses his wife and hopes she is found okay."
Authorities are intensifying their search for the mother, whose car was found abandoned last month along a state highway in what police suspect may have been a scene staged to look like an abduction.
Waller had just attended the June 1 divorce hearing, according to police, and drove to her husband's home at around 4:00 p.m. to pick up her 5-year-old son, Maddox.
But the child was not at the home when Waller arrived and family members say they believe her husband, a former police officer, lured her to the home to kill her.
"It was just his bait to get her to the house so he could kill her," the woman's sister, Cheryl Brenneke, said in an interview with FoxNews.com.
Jackson Police Chief James Humphreys described Clay Waller as a "person of interest" in the case and said authorities uncovered potential evidence from his home, though Humphreys declined to elaborate on what was found.
"He was the last person to see her and be with her," Humphreys told FoxNews.com. "We suspect foul play -- no question."
Clay Waller told investigators that he and his wife had an argument at his home before Jacque "walked away mad," according to Humphreys.
Police found Jacque Waller's car abandoned along Interstate 55 in Missouri the morning after she was reported missing. Waller's purse, keys and cellphone were not found inside the vehicle, and Humphreys said there has been no activity on her credit cards and phone since her disappearance.
Humphreys said the car – a Honda Pilot – was found with a flat tire. He said the tire is being analyzed to see whether it was intentionally made flat.
"We've not been able to eliminate him at all," Humphreys said of Waller. "And we don’t believe it was an abduction-type thing off the Interstate – it may have been made to appear that way."
The Jackson Police Department -- with the help of the FBI -- has scoured land and water in the surrounding area for any trace of Waller.
On Monday, a woman reported finding Jacque Waller's Blue Cross Blue Shield business cards along another state highway about 8 miles from where her car was recovered. Waller worked as a manager for the health insurance company.
Brenneke, who has custody of her sister's three children -- Maddox, Avery and Addison -- told FoxNews.com that Clay Waller threatened to kill his wife if she filed for divorce and harassed her with repeated phone calls and text messages after she moved out of the couple's home in March.
"It was just non-stop calls and texts and showing up at her work every day," Brenneke said, adding that her sister never went to police because she feared he'd kill her if she did.
"She just wanted out," Brenneke said of her sister, who had been staying with her at her home in St. Genevieve after the couple separated.
Lt. David James of the Cape Girardeau County Sheriff's Department described Clay Waller as "less than cooperative." He said Jacque's business cards will be analyzed for fingerprints and kept as potential evidence.
"She didn't walk away from her life," James told FoxNews.com. "She didn't just leave her triplets."
A $3,500 reward is being offered for any information leading to Jacque Sue Waller's whereabouts. She is described as 5 feet 2 inches tall and weighing 135 pounds.
Anyone with information on her disappearance is being urged to call the Jackson Police Department at 573-243-3151.
Fox News' Cristina Corbin contributed to this report.