A divorced dad-of-two posted a smiling selfie with his kids on Facebook just an hour before shooting them and dead and taking his own life.
Humberto Christian Tovar appeared happy in the snap with beaming Valeria, 12, and Matias, nine, taken in his car in Miami Lakes, Florida, USA.
But soon after, the 41-year-old and his children were dead.
The kids' mum Jessica Forero Cardona came upon the scene by a canal around 9pm on Tuesday and desperately tried to resuscitate her son and daughter.
Her screams were said to reverberate through the quiet neighbourhood.
Tovar and wife of 12 years Jessica divorced in August last year.
Tovar's mum Luz Kuznitz told Local 10 News : "He was dealing with bipolarity. He didn't take his pills.
"He never took care of it. He never wanted to take medication therapy."
She added that her son - who worked at City Bikes in Aventura - was a keen cyclist and would often bike to help relieve stress.
Luz said she once asked if he was capable of harming his children and he said: "No, never, absolutely not."
Jessica had become worried as it got later into the evening and she hadn't heard from her children, as they had school the next day.
Tovar had picked them up from her house earlier, according to Miami-Dade police.
She later found their bodies on some grass next to a concrete bench.
The Miami-Dade Police Director Alfredo 'Freddy' Ramirez III confirmed the deaths on Twitter, writing: "Earlier this evening, officers responded to the scene of a shooting where a father senselessly shot and killed his 12-year-old daughter and nine-year-old son before killing himself."
A GoFundMe has been set up, aiming to raise $25,000 (£18,400) to help Jessica afford the funeral costs and mental healthcare.
Madga Peña's Ring doorbell picked up the mother's cries.
She told WSVN : "I just opened the door and I ran. My son ran behind me. He didn't even have shoes.
"I ran across the grass and when I got there I saw the ladylike on top of the little boy.
"I couldn't see the dad or the daughter because of the darkness at first."
Magda went on to describe to NBC 6 Miami how Jessica pulled the children's bodies together in her efforts to do chest compressions on them both.
"At that point, I was crying already, I think I went into shock cause I was just like freaked out, I don't know," she said.
Magda also helped with compressions and said she saw the gun lying on the ground.
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