The jury in the trial of Michelle Camire, a mother accused of killing her infant son, heard a recording of an emotional 911 call in a Winnipeg courtroom Tuesday.

Camire, 25, has pleaded not guilty to manslaughter in the death of Michael Helgason, one of her three-month-old triplets. The boy died of head injuries in October 2004.

In the five-minute recording played Tuesday, Camire is heard sobbing to the 911 operator on a call received just after 11 a.m. on Oct. 22.

"My three-month old baby, I've killed him," she cries, then struggles to answer questions about her address and whether the baby was breathing.

"I was tired and frustrated earlier and I slammed him down when I put him down," she says. "I'm going to go to jail, aren't I?

"He's gone, he's gone, I know he's gone," she says, then begins to sob.

The operator inquires about the sound of a child talking in the background, and Camire says it's her 20-month-old daughter.

"Oh my God, what has mommy done?" she says. "How am I going to tell your daddy this?"

The 911 operator transfers the call to a paramedic, who asks Camire what happened.

"My baby was crying earlier today. I got mad and I got frustrated and I slammed him down when I put him down and now he's dead."

The incident happened "almost two hours ago," she says.

The paramedic urges Camire to keep calm.

"I'm going to tell you how to help your baby," he says, and leads Camire through first aid and mouth-to-mouth resuscitation.

As emergency responders arrive, Camire again tells the operator, "I can't believe I did this to him."

"You can hang up. You did a good job," the operator says.

"No, I didn't, but thank you," Camire says.

Firefighter found Camire crying over baby

Bradley Mazor, the first Winnipeg firefighter to arrive at Camire's North Kildonan townhouse, told the court he found Camire on her knees over the baby, crying.

Mazor said he asked Camire how her baby had stopped breathing.

She told him she was frustrated and threw the baby down onto the bassinette or into the bassinette, Mazor testified.

The firefighter said he could tell from the baby's colour that the child was in trouble.

The infant, Michael Helgason, was pronounced dead later in hospital.

Crown attorney Brian Bell has alleged Camire slammed the child's head into a bassinette, then found him unresponsive about two hours later before calling for help.

Camire's trial is expected to last two weeks.