In act 4 scene 7, the Queen reports that Ophelia has drowned. While it seems that initially this began as an accident (she was in a willow tree overhanging a brook and decorating it with flowers when the branch snapped and fell into the water), it seems that her recent madness creates a suicidal motivation for the accident. While her clothes held her up for a while:
She chaunted snatches of old lauds,
As one incapable of her own distress,
Or like a creature native and indued
Unto that element; but long it could not be
Till that her garments, heavy with their drink,
Pull'd the poor wretch from her melodious lay
To muddy death. (7.7.195–201)
Upon hearing the news, Laertes doesn't really place the blame on anyone, simply stating that he will not cry because sister has already had enough water.
Act 5, scene 1, is Ophelia's burial scene, and Hamlet is completely unaware of her tragedy until Laertes shows up and refers to "[his] sister" in a conversation with the priest. Hamlet becomes distraught watching...
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