Two years ago, twin sisters Carla Merhige and Lisa Knight volunteered at Miami's juvenile lockup, singing as a duet in front of dozens of troubled girls during Christmas.

Lisa, with her country twang, and Carla, with the more soulful voice, performed before scores of girls who were awaiting trial.

On Thursday, the voices of the two 33-year-old women were silenced forever.

Police say their brother, Paul Michael Merhige, gunned them down, also killing two other relatives -- his aunt, 76-year-old Raymonde Joseph, and 6-year-old Makayla Sitton -- at a family Thanksgiving gathering in Palm Beach County. Injured were two others, including Lisa's husband, Patrick Knight, 37. Authorities said Lisa Knight was pregnant. The motive was unclear.

Police fanned out across South Florida in search of Merhige late into the night Friday. Merhige, 35, who lived in Kendall, had fled in a blue 2007 Toyota Camry.

Little is known about him, though friends said Lisa Knight often spoke about her brother and the wonderful times they had together as kids. He graduated from Gulliver Prep and the University of Miami.

On Friday, friends of both women -- who had been born and raised in Miami -- mourned the violent end to their lives, filling the Facebook walls of the sisters with condolences.

The twins were ``inseparable,'' speaking on the phone several times daily, spending holidays together and going on joint family vacations, said Sonia Ferrer, the director of Miami-Dade's Guardian-ad-Litem Program, where Carla worked.

``They each made each other whole,'' Ferrer said. ``Carla was very proud of her sister's accomplishments, and her sister was very proud of Carla.''

Said Miami-Dade Circuit Judge Cindy Lederman, who helped arrange the holiday season concerts: ``[Singing] was a gift they had, and they shared it with everyone -- especially the children. I never saw the two sisters without a smile.''

``They were the loveliest human beings you ever could meet,'' Lederman said. ``This is so sad.''

The sisters had ``angelic'' voices, often singing at courthouse holiday parties. They also sang at their church, Our Lady of Lebanon on Coral Way, and at funerals, weddings and other occasions, friends said.

The sisters went to Epiphany Catholic School -- where they sang duets in elementary school talent shows -- and then Our Lady of Lourdes Academy.

Lisa graduated from the University of Miami, where she later got an MBA; Carla from Florida International University.

Lisa Knight left a job at the Miami-Dade County courthouse a few years ago to work with her mother at Coldwell Banker in Pinecrest. She was remembered as a devoted friend, who always had time for others and was knowledgeable beyond her years.

``If you wanted advice she'd always have an ear for you to talk and basically be a friend,'' said Miguel Arellano, a real estate agent at Coldwell Banker. ``She always had wonderful advice for people. She was very caring and loving.''

Her husband, Patrick Knight, is a litigation attorney and motivational speaker.

Colleagues of Carla Merhige, a children's advocate who spent nine years at the guardian's office and recently started a new assignment working with adolescents aging out of the foster care system, described her as dedicated to children and families -- and a wonderful co-worker.

On Wednesday, Ferrer said, Merhige worked late into the evening to make sure that a Thanksgiving donation from the mayor of Doral got to 35 needy families in time for the holiday.