Updated

Two Pennsylvania parents have been charged in the death of their toddler son who suffocated when they allegedly tied a mattress on top of his crib to keep him from climbing out.

The couple, Justin J. Dwyer, 29, and Courtney Stash, 28, was charged Wednesday with involuntary manslaughter and aggravated assault in connection with their 2-year-old son Eoin’s April 25 death.

Cops said the parents were using bungee cords and heavy bags of driveway salt ice melt to keep the mattress on top of the crib and prevent the boy from climbing out -- but neither parent initially told police about those measures, authorities said.

Police said they only learned that information when Stash’s 8-year-old son revealed it to detectives several days after Eoin’s death.

The autopsy in the case lists the official cause of death as asphyxia due to “entrapment between the crib and overlying twin mattress secured by bungee cording.”

The couple’s lawyers did not immediately return requests for comment.

Stash called 911 after finding Eoin unresponsive inside his crib in the master bedroom, but the toddler was already dead when emergency responders arrived to the family’s home in Myerstown, Penn., according to police.

According to the arrest affidavit, Stash told police she found her son “standing/leaning and slumped over a top railing.” He was not breathing, so she then brought the boy to the living room where she performed CPR.

Stash’s son told detectives that for a few weeks, the two covered the crib with a blue mattress to keep Eoin from climbing out. In recent instances, they had begun placing “ice bags” on top of the mattress to weigh it down and fastening it with a red cord with hooks on the ends, he said.

The baby eventually could push the weighted mattress down, so they started fastening it with bungee cords, a detective said.

Investigators said they recovered the mattress, two 50-pound bags of ice melt driveway salt and a red bungee cord from the master bedroom.

The morning of Eoin’s death, before emergency help arrived, Dwyer and Stash spoke about the mattress trapping Eoin by the neck, according to a follow-up interview with the 8-year-old boy.

Bail for the couple was set Wednesday at $250,000 each.

The Associated Press contributed to this report