Bobby was killed off on "9-1-1" because it was a creative decision by the show's producers to offer a powerful and authentic storyline. He died from exposure to a lethal virus (a mutated strain of Crimean-Congo hemorrhagic fever) after a biolab explosion, choosing to give the only available vaccine dose to a colleague instead of saving himself. This decision had been planned for some time to bring weight and realism to the show, highlighting the life- and-death stakes faced by first responders and profoundly affecting the character arcs of the others. It was not related to actor Peter Krause wanting to leave, but rather a narrative choice to provide a meaningful and emotional farewell that impacts the entire team going forward.
The showrunner Tim Minear explained that Bobby's death was intended to be a significant and clear-cut event to emphasize the dangers first responders face and to prevent the series from remaining too comfortable without stakes. Bobby's character arc, which included seeking redemption and struggling with a death wish, culminated in this heroic sacrifice, making his death feel natural within the story. It was also designed to leave room for the other characters to grieve and develop in the wake of this loss.
