Sandy Hook Victim's Father Pens Open Letter to Dad of Student Killed in Santa Barbara Massacre

As families try to make sense of the deaths of their children from a man who went on a shooting and stabbing rampage in Santa Barbara, one Sandy Hook father wants them to know they are not alone.

Mark Barden, who lost his 7-year-old son, Daniel, in the 2012 Sandy Hook school shooting, penned a letter to Richard Martinez.