Thanks Umar, for sharing the news.
Real reason behind this collapse would be known in future sometime. It may be due to some structural design discrepancy, some overlook during the construction phase design, or something unusual happening with the structure after completion of construction. However, this type of disasters in an advanced country like USA, where engineering design & construction procedures and practices may be termed state-of-the-art, remind us (the engineers) to be very very careful during both the design and the construction phases of a public facility, in order to avoid such disasters in future, to safeguard loss of valuable lives & to avoid a bad name for the engineers community.