The suspect was harshly interrogated until he confessed.

Literal

Suspect [topic-は] confess-[until-まで] severe interrogation [object-を] received.

~まで ('until') marks the endpoint. きびしい ('severe / harsh') modifies 尋問. 尋問 ('interrogation / questioning') + 受ける ('receive') parallels 手術を受ける / 試験を受ける — 受ける is widely used for undergoing procedures. All formal legal vocabulary.