Two mothers sat on either side of the gallery inside a Calgary courtroom today, each hoping for a very different outcome. 

One is the mother of Juliano Vieira, a Grade 11 student who died after being punched, kicked and stabbed by a group of partygoers in March 2014. The other is the mother of one of two teens charged in connection with his death. 

It marks the beginning of the manslaughter trial for both young men, who cannot be named under the Youth Criminal Justice Act.

It all started around midnight on March 8, 2014, in the southwest community of Braeside when the host of a high school house party asked everyone to leave.

It was at that point an argument between two groups of friends turned violent, according to the Crown prosecutor's opening statement.

Within those groups, were teens with a history "bad blood" between them. 

"Although it didn't start out with Juliano being aggressive towards anyone, he quickly became the target of a larger group's aggression," said prosecutor Katherine Love.

One of the teens dragged the victim to the ground by his hair and "bombarded Juliano with a flurry of punches," said Love. The other, she said, chased him and hit him with a baton.

The teens on trial were 16- and 17-years-old at the time of the attack. They are represented by defence lawyers George Sirois and Ian McNish.

The trial is scheduled to last all week. 

Two others are charged in connection with his death, both of whom were above the age of 18 when Vieira was killed. 

Trent Hynne is charged with second-degree murder and attempted murder, and Roland Smith has also been charged with accessory after the fact to murder and carrying a concealed weapon.