Police say Monday's holiday mass shooting had been planned for weeks.

Seven people died and dozens were injured as Robert Crimo III fired as many as 70 rounds into the crowd from a Highland Park rooftop. The shooter accessed the roof via a fire escape ladder, then fled the scene wearing women’s clothing. 

An AR-15-type weapon was used n the assault, but police say Crimo bought the rifle used in the deadly shooting legally — along with four other firearms.   

Joining Nancy Grace today:

• Lisa Fine-Cavalli, Vegas Mass Shooting Survivor (Oct 1, 2017), Co-Founder: Route91Strong, Twitter: @LisaFineLove, Facebook.com/Route91Strong
• Dale Carson - High Profile Attorney (Jacksonville), Former FBI Agent, Former Police Officer, Author: "Arrest-Proof Yourself, DaleCarsonLaw.com
• Dr. Jillian Peterson - Forensic Psychologist, Professor of Criminal Justice at Hamline University (St. Paul, MN), Expert on Mass Shootings and Violence Prevention, Author: "The Violence Project: How to Stop a Mass Shooting Epidemic", theviolenceproject.org, Twitter: @JillKPeterson,
• Dr. Michelle DuPre - Former Forensic Pathologist, Medical Examiner and Detective: Lexington County Sheriff's Department, Author: "Homicide Investigation Field Guide" & "Investigating Child Abuse Field Guide", Forensic Consultant, DMichelleDupreMD.com 
• David Katz - Former Senior Special Agent with the DEA, Founder and CEO: Global Security Group, Inc., Active Shooter Response Expert,
• Lynn Sweet - Washington Bureau Chief, Chicago Sun-Times, Witness at Fourth of July Parade