LOS ANGELES (KABC) -- An actor best known for his role on the "Power Rangers" television series pleaded guilty Thursday to manslaughter in the killing of his roommate in 2015, officials said.Ricardo Medina, 38, of Green Valley, killed his roommate with a sword after an argument over Medina's girlfriend on Jan. 31, 2015, officials said. The victim, 36-year-old Joshua Sutter, was stabbed 10 times.The two got into an argument that escalated into a physical fight at a house they shared in Green Valley. Investigators said Sutter followed Medina and his girlfriend into their room, forcing the door open. Medina then stabbed Sutter with a sword he kept in the bedroom.Medina's attorney claimed the stabbing was in self-defense. After his initial arrest, Medina was released when the District Attorney's office declined to file charges.After additional investigation, he was charged with murder in January 2016.Medina has entered a plea to one felony count of voluntary manslaughter and admitted an allegation of using a sword in the killing.Since her brother's brutal death, Rachel Kennedy has spent more than two years on a quest for justice. She said Thursday was perfect because her brother would have turned 38.Sandra Vasquez was a close friend of Sutter, and a dear friend of Kennedy. She said Thursday marked a new chapter."I don't think it's closure. I think it's all a celebration of beginning to live," she said.Both believe Kennedy's persistence in the case finally paid off when Medina pleaded guilty."It's worth it. It was so worth the fight," Kennedy said.The actor faces six years in state prison, with sentencing scheduled for March 30, according to the Los Angeles County District Attorney's Office.Medina played the Red Lion Wild Force Ranger in 2002 for the TV series and had additional voice roles in later video games and TV episodes related to the Power Rangers, according to IMDB.