Coloradans Randy and Tammy Harris had been planning the trip for 10 months. Seven-year-old son Jackson had his heart set on Space Mountain; his 4-year-old sister, Anabelle, was hoping to meet her namesake from Beauty and the Beast.

They'd come to experience what's billed as the "Happiest Place on Earth". And then, just a few miles away, there was another superlative: The deadliest mass shooting in modern US history.

The Harrises are certainly not insensitive to tragedy. They live in Aurora, Colorado, where a man dressed in black body armor rampaged through a movie theater in July 2012, killing 12 and wounding 70 others.