A Winnipeg court has begun hearing the trial of two teenagers accused of gunning down two other teens at a house party in 2009.

The two accused, who are both charged with first-degree murder, were 16 and 17 years old at the time of the incident and cannot be named under the Youth Criminal Justice Act.

Matthew Reynolds and Tyler Hawula, both 18, were shot and killed at a home in the 400 block of Martin Avenue just after midnight on Dec. 5, 2009.

Another male, who was 17 years old at the time, was wounded.

Police have said the two accused had been kicked out of a party at the Elmwood-area house, but they came back with two other suspects.

As the trial of the two accused men began Monday in a Winnipeg courtroom, the court heard audio recordings of the 911 calls that were made that night.

Reynolds's sister, Anita, told reporters it was difficult to hear the panic and screaming from those calls, as well as come face to face with the two accused.

"I felt bad for all the people that were actually at the party and had to sit there and see what happened, and the people that had to make phone calls," Anita Reynolds said outside court.

The sister added that their mother had to leave the courtroom at one point because she could not listen to the 911 recordings.

"For us to sit there and look at them and to hear all the phone calls and what's coming up next, it's going to be super hard," she said.

A third accused person pleaded guilty to manslaughter in connection to the deaths in January.

The fourth accused, a youth, has a preliminary inquiry scheduled for April 2013, according to justice officials.