この度はご愁傷様でございます。心からお悔やみ申し上げます。 — I offer my heartfelt condolences for your loss. (Cultural · Religion, Formal to Acquaintance, JLPT N3)

Gesture & etiquette

Bow deeply (about 45 degrees) when offering condolences; speak in a low, subdued voice; wear dark/subdued clothing if attending a funeral; do not use congratulatory words or expressions even inadvertently.

ご愁傷様' (goshuushousama) is the standard formal condolence phrase spoken directly to the bereaved; 'お悔やみ申し上げます' can also be used in written condolences; avoid 'たいへんでしたね' in bereavement contexts as it sounds too casual.