Horrific. Parents were probably trying to give their child an enjoyable evening, and it ends in tragedy. Terribly sad.
An enjoyable evening for a toddler does not include watching a professional sporting event from a luxury suite, or any other seating. The term for a young child at such an event (or in a movie theater, or on a floating party barge) is "dragged along."
And yes, it is a terrible tragedy. I'm so sorry this happened to the child and his surviving family.