A Florida mother who killed her own mother and two of her young daughters before taking her own life had argued with her husband about pornography on his phone in the days leading up to the killings, police said.

Hailey Dempsey, 27, shot her 55-year-old mother, Valerie DeBoe, in the early hours of May 3 at the family’s home in Plant City, near Tampa.

She then left the house with her three young daughters. Authorities said Dempsey later killed her 4-year-old and 4-month-old daughters and fired at her 2-year-old daughter, but missed. She then died by suicide.

Plant City Police Chief Richard Mills said Thursday that officers had responded to the family’s home three times in the two days before the killings.

The first call came May 1 following what police described as a verbal argument between Dempsey and her husband, Jay, after she discovered pornography on his phone.

“It wasn’t cheating or anything like that, evidently it was just porn, and they were having an argument over that,” Mills said. He added that investigators believe the dispute may have been connected to the events that followed.

However, officers who responded to the initial call found no indication of violence or criminal activity at the time.

Later that day, Dempsey contacted police again because she believed a tracking device might have been placed on her vehicle. Officers searched the vehicle but found nothing.

Dempsey subsequently left the home with her three daughters and her mother, who had been visiting from Clearwater. They spent the night at a hotel.

The next day, police accompanied Dempsey back to the family home while her husband was away so she could collect clothing.

Mills said the couple later met at a local library for a private conversation.

After the killings, Dempsey’s husband was temporarily detained while investigators examined whether he had any involvement. Police ultimately determined that he was not a suspect, and he was never arrested or charged.

Investigators also said there were indications that mental illness may have played a role in the tragedy.

The case remains a devastating example of how quickly a domestic dispute and apparent mental-health crisis can escalate into an unimaginable tragedy.