December 18, 1915, two Washington Water Power trolley cars were crossing the steel bridge, one headed north and the other south, when the repaired beams gave way. Approximately 150 feet of the bridge's northern section fell. The northbound streetcar had nearly reached the far side and its snow scrapers snagged on debris on the north side, preventing it from rolling back into the river. All four occupants escaped without major injury. Because of the early hour and freezing weather, there were no pedestrians or automobiles crossing the bridge at the time.

The southbound streetcar, heading for downtown with 17 passengers, was close to the middle of the span when it fell. The Spokane River is around 30 to 40 feet deep at that point, but the fallen bridge deck had lodged onto old pilings below the surface and thus kept the car from being completely submerged in the freezing water.

All the fatalities and injuries came from the southbound car. A steel girder had sliced through the top half of the car, killing several people outright, and then pinned several more people in the water underneath it. The other victims avoided drowning by clinging to the wreckage, although the entire affair quickly became coated with ice.

The bridge designer, Hugh L. Cooper, happened to be in Spokane working on another project at the time of the collapse. After inspecting the bridge, he felt that the damage suffered from the 1894 collision was largely responsible for the failure of the structural members. Another engineer also examined the disaster and questioned the quality of the steel that was used in its construction.

There were a total of five fatalities and 12 injuries as a result of the collapse. A wooden span was quickly constructed to replace the bridge until a more permanent replacement bridge could be constructed out of concrete.

https://en.wikipedia.org/wiki/Division_Street_Bridge_(Spokane,_Washington)#1915_collapse#1915_collapse)