The trial has begun for a self-proclaimed white supremacist charged with second-degree murder in the death of a Calgary man.

Mark Mariani

Mark Mariani was beaten to death in an alley in 2010. The Crown says he was in the wrong place at the wrong time when he met the men who killed him. (Handout)

The Crown alleges Mark Mariani was beaten to death after wandering into an alleyway where Robert David Reitmeier and another man were spray painting graffiti.

The second man, Tyler Sturrup, pleaded guilty to second-degree murder and was sentenced to life in prison with no chance of parole for 10 years.

Police believed Mariani was beaten in the alley behind a strip mall at the corner of 16th Avenue and 15th Street N.W. before collapsing by his car in a parking lot.

Reitmeier sat silently as the the Crown outlined its theory about what happened in that northwest parking lot in 2010. The Crown says after being repeatedly kicked and stomped on, Mariani crawled to his car but died without being able to get in or call for help.

The video of the gruesome crime scene was played Monday afternoon for the jury. It showed Mariani's brutalized, lifeless body lying in a pool of blood.

The Crown said he was simply in the wrong place at the wrong time — the victim of a seemingly random, unprovoked attack.

Victim's sister makes emotional statement

Kathy Weltzin, the victim's sister, fought tears as she described the worst day of her family's life being the day Mariani died.

hi-cgy-neonazi-reitmeier

Robert David Reitmeier, who has ties to neo-Nazi groups, is facing second-degree murder charges. (Courtesy of Calgary Herald)

"It's very sad because we have to relive it again.... We just still don't know why, we want answers about why Mark had to die that day," she said.

"Mark was such a loving soul."

The 47-year-old had struggled with Crohn's disease — it had weakened Mariani but he was just starting to get healthy.

Weltzin said it is important for Mariani's family to attend the trial to support the court process.

"We're here in spirit for Mark," she said. "We want Mark to know we tried everything we could to bring justice for him."

The trial is expected to last for three weeks.