Melanie Lyons' grandmother says the four girls charged in her granddaughter's stabbing were looking to fight the 15-year-old's sister. The four girls (a 12-year-old, two 13-year-olds, and a 14-year old) have been arrested. One of the girls is charged with second-degree murder and the other three are charged with principal to second-degree murder.

Footage of the stabbing, which was posted on Facebook and Instagram live, shows one girl armed with what appeared to be a knife as the victim approaches and lunges at her. Video shows the group of girls fleeing the store in a getaway car as one of them screams, “Just stabbed somebody at Walmart.”

Joining Nancy Grace today:

• Yolanda Lemonia - Grandmother of Victim
• Wendy Patrick - California prosecutor, author “Red Flags” www.wendypatrickphd.com 'Today with Dr. Wendy' on KCBQ in San Diego
• Dr. Jenn Mann - Marriage and Family Therapist, Host 'Couples Therapy' on VH1, "The Dr. Jenn Show” on Sirius XM, Author: "The Relationship Fix." 
• Robert Crispin - Private Investigator “Crispin Special Investigations” www.crispinsinvestigations.com
• Dr. Tim Gallagher - Medical Examiner State of Florida www.pathcaremed.com
• Phil Chalmers - True crime writer, Counter Homicide Trainer, Criminal Profiler, Author: “Inside the Mind of a Teen Killer” and “The Teen Killer Whisperer.” 
• Stephanie Pagones - Digital Reporter, FOX Business & Fox News, @steph_pagones,