From the testimony of an accused killer-turned-star witness, to the slain Belmont mother's teen having a nervous breakdown in court, Week 3 in the murder trial of Lesandro "Junior" Guzman-Feliz was filled with powerful moments.

Kevin Alvarez took the stand Monday, the first suspect arrested in this case who was infamously captured on video dragging Junior from a Belmont bodega and to his death at the hands of armed gang members last June. Alvarez broke down in tears as he described his role in the murder, saying he punched and kicked Junior while he was down.

Alvarez, who identified each of the five suspected killers on trial, testified that members of the Los Sures set of the Trinitarios came upon a frightened Junior in their rival sunset chapter's territory. He told jurors, "The only thing I heard him say is that he wasn't Sunset," referring to Junior's alleged remarks.

Alvarez said he believed Junior was a rival gang member at the time, but had no direct knowledge that he actually was.

Then on Tuesday Alvarez testified that after the stabbing the gang returned to leader Diego Suero's home, where a photo was pulled out that was entered into evidence. Alvarez says Los Sures and Bad Boys members gathered around trying to figure out which "Sunset member" they had just stabbed, but neither of the men Alvarez pointed to were Junior, and he acknowledged that.

The details of the Alvarez plea deal were also revealed. He pleaded guilty to manslaughter and conspiracy -- agreeing to provide truthful testimony for the chance to walk away with only "time served" on the conspiracy charge when all is said and done.

On Thursday, Junior's mother had to be removed from court after having a nervous breakdown. She says the outburst was a result of seeing video she had never seen before, showing bodega employees open a counter door that allowed Alvarez access to her son.

Defense attorneys cross-examined Alvarez, pointing out that he was the only attacker out of the whole group who worked hard to breach the barrier that Junior was hiding behind to pull him out -- knowing the gang members outside were armed.

Alavrez says he didn't expect his Trinitarios brothers to use their weapons, and expressed regret after finding out Junior had died -- and is now testifying for the victim's family to get justice.

The trial resumes Tuesday.