The Kings Park man on trial for killing his infant son wept Tuesday at the defense table after he and jurors heard a recording of the chaotic 911 call when the baby was found blue, stiff and not breathing.

Christopher Foster, 32, is charged with second-degree murder and manslaughter in the Oct. 11, 2011, death of his 43-day-old son, Jonathan Hertzler. Prosecutors say Foster never wanted the child and caused the infant's death by fracturing his skull and several other bones. The trial is before state Supreme Court Justice William Condon in Riverhead.

The baby's grandmother, Barbara Hertzler, called 911 from the Ronkonkoma apartment she shared with her daughter, Clarissa Hertzler, Foster and the baby.

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Clarissa Hertzler can be heard howling in anguish in the background.

"I don't understand what happened," Barbara Hertzler said on the recording, apparently to Foster. "What did you do?"

"I didn't do anything!" he replied.

"My grandbaby's dead," Hertzler told the 911 operator. "I don't know what happened. He was laying on his belly, and he's blue."

A dispatcher instructs her on how to perform CPR, and then Foster takes over the phone to relay instructions to Clarissa Hertzler.

"Please don't stop, please!" he told her as the ambulance crew arrived. "Baby, please, keep going!"

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Operator Debra Grabowski said the call came at 6:41 a.m. That was an hour and 10 minutes after Foster called his boss at the time, Leonard LaRosa. LaRosa testified that Foster's 5:30 a.m. call woke him up.

"He said that the baby was not breathing," LaRosa said during questioning by Assistant District Attorney Dana Brown. "He said the baby was blue. I said, 'Why are you calling me? Call 911.' "

Emergency medical technician Gary Stadler broke into tears as he described his inability to get the baby to breathe or have a pulse after he got to the apartment. He said he noticed a dime-sized bruise on the boy's left temple.

In his opening statement Monday, defense attorney David Besso of Bay Shore said there is no evidence against his client and suggested that Barbara Hertzler, a schizophrenic later hospitalized when she said she wanted to kill people, could be responsible.