It was when she was walking home after dropping her 7-year-old at the bus stop to go to school that she made the decision.
She would drown her 3-year-old and 6-year-old sons.
Drown them so she could be a better mother to her oldest son, aged 7.
And so, a court has heard, this 40-year-old mother arrived home and sent her two boys to take off their pyjamas, Superman for Luke, Spider-Man for Daniel.
A short time later she made the call for help, reports news.com.au.
"Um, my two sons," Laurel Michelle Schlemmer told emergency services in April 2014.
"I think that they've, they've drowned in our bathtub."
"OK, tell me exactly what happened," the call-taker said.
"I, uh, let my 6- and 3-year old sons play in the bathtub a little bit before their bath this morning," reports The Post Gazette.
"And, uh, I was, and then I went to, to the restroom and, um, took longer than I should have or planned and then I came back. They're unconscious."
"Are they breathing?"
"It doesn't look like it, sir," she said.
Mother-of-three Laurel Schlemmer is currently on trial for the murder of her two young sons. The Pittsburg woman, described as leading a normal, quiet life before her two sons drowned, entered the court handcuffed on Wednesday (US time).
In her opening statement Allegheny County Assistant District Attorney Lisa Pellegrino told the judge that when police arrived after that 911 call they found Daniel and Luke laid out on the floor, dry and with their hair combed.
Schlemmer had changed out of her wet clothes and had deposited them and two towels in the garage.
Pellegrino says that Schlemmer had put each boy facedown in the bath then sat on them.
"She thought she'd be a better mother to Joshua if her other two children would go to heaven," Ms Pellegrino said.
In a videorecorded interview, Schlemmer told police "voices" told her to do it reports CBS News.
"These crazy voices were prompting me to act irrationally, and I changed clothes, and I got in there with them and held them underwater, and I felt like I was looking down on the whole thing - just kind of out of body. And then I freaked out and got out and changed my clothes and got them out," she said.
Three-year-old Luke was pronounced dead at the scene, his older brother, Daniel, 6, was rushed to hospital but died four days later.
At the time of the drowning their dad, Mark, was at work and about to receive the most horrific call he could imagine.
The family, active in the local church, had been under scrutiny before.
A year before Schlemmer was accused of drowning two of her sons in the family bathtub, she ran them over with her mini-van.
The court heard that on April 16, 2013, Schlemmer took the boys, Luke, then 2, and Daniel, then 5, to her parents' house. When the mother-of-three pulled into the garage she let the boys out.
Prosecutors say she then tied the boys with twine and put them behind the van.
Schlemmer then put the vehicle in reverse "and drove over them - not once, not twice, but three times," said Ms Pellegrino.
Luke suffered a jaw fracture, a liver laceration, a pancreatic injury and a fractured ankle. Daniel had a broken pelvis.
The Sun reports that police and a hospital nurse said the boys had tire tracks on their abdomens.
And in 2009 a police officer testified Schlemmer received a "ticket" after she left Daniel alone in a parked car on a hot day.
Police used a heat sensor to determine the car was 44C inside. Daniel was locked in for 20 minutes.
Lawyers acting for Schlemmer have said that they will show the court Schlemmer was insane or operating under diminished mental capacity when the drownings took place.
The trial continues.