The children were killed either Aug. 12 or Aug. 13, according to the criminal complaint against Chris Watts.
>> Related story: Shanann Watts’ girls may have been dead when she got home, husband’s charges show
The seemingly happy family had taken a trip to North Carolina to visit Shanann Watts' family shortly before the homicides. The vacation apparently included a trip to Myrtle Beach, South Carolina, where Michele Greer, of Fayetteville, told CBS17, in Raleigh, that she, her husband and their own three sons ran into the Watts family.
Myrtle Beach is about 130 miles away from Aberdeen, where Shanann Watts’ family lives.
Greer told the news station that she and Shanann Watts, 34, struck up a conversation as they waited in line for their respective children to play on a bungee trampoline.
“We just started talking about our kids,” Greer said.
Greer told CBS17 that Shanann Watts expressed excitement about her pregnancy, which she hoped would result in a baby boy. Family and friends have said that Shanann and Chris Watts planned to call their son Niko.
"She said, 'This pregnancy is just like my first two pregnancies. It's probably another girl,'" Greer told the news station. "I said 'No, maybe not.'
“The last thing I told her was, ‘Good luck to you.’”
Greer said it was 11 days later, back home in Fayetteville, when she learned that Chris Watts was suspected of killing his wife and daughters.
"As soon as my husband got home I said, 'I think this is the couple we met at Myrtle Beach.' He said, 'No, I'm 100 percent positive this is the family,'" Greer said.
Grabbing her cellphone, Greer looked at the photos she’d taken of her sons that day.
In the background of one photo, Shanann Watts can be seen taking photos of Bella on the bungee trampoline. Her father, Frank Rzucek, is standing at her side.
Partially hidden behind Shanann Watts appears to be her husband, Chris Watts.
"Chills. Heartache," Greer said of her discovery. "I'm sickened that a parent, a father, could do that to his children and to his wife."
Chris Watts, 33, was charged Monday with five counts of first-degree murder -- including two for killing a child under the age of 12 while the defendant was in a position of trust, one count of unlawful termination of a pregnancy and three counts of tampering with a deceased human body. He is being held without bail in the Weld County Jail.
In a confession to police, Chris Watts alleged that his wife strangled the girls after he told her he wanted a separation. Though he initially denied it, he admitted to detectives last week that he'd been having an affair with a female co-worker.
Chris Watts said he "went into a rage" and strangled Shanann Watts after seeing her strangling Celeste on the feed of their baby monitor, an arrest affidavit said. He admitted disposing of their bodies, which were found a week ago on property belonging to Anadarko Petroleum Corp., the company Chris Watts worked for before his arrest, at which time he was fired.
Shanann Watts’ body was found buried in a shallow grave near two large oil tanks, authorities said. Bella and Celeste were found inside the tanks, submerged in crude oil.
Court documents said the girls' bodies had been submerged in oil for four days.
Greer told CBS17 that she does not believe the claims against Shanann Watts made by her jailed husband, who she said was silent that day in Myrtle Beach.
"The way they just smiled at (Shanann). The way she was filming them," Greer reasoned. "She loved those girls, and those girls loved her."