What Did Jack Do?

Dressed up in a formal suit, evoking memories of Twin Peaks (1990)' Special Agent Dale Cooper, David Lynch's hard-boiled, chain-smoking detective probes into the personal life of inscrutable Jack Cruz: a suspect related to a hideous crime of passion. Now, against the backdrop of a gritty, black-and-white railroad station café, and a ceaseless battle of wits, the masterful interrogator presses Jack to confess to the murder of Max Clegg; however, his evasive answers prove that Jack is a hard nut to crack. But, there is an elephant in the room. So, let's dispense with the formalities and start talking turkey. What did Jack do?