The true measure of a person is not how they lived but how many lives they touched along the way.  Zach Sobiech, who passed away in May from cancer, touched thousands of lives, and they all showed up to honor his memory.

5000 people crowded into the Mall of America this weekend to sing 'Clouds,' the song Sobiech wrote to say goodbye. Watch the emotional tribute.

NEXT: Celebrities Create 'Clouds' Video

Celebrities Music Video Singing Dying Teen's Song 'Clouds'