I Was Jack Mortimer.

The jealous star conductor Montemayor knows that his beautiful younger wife, Winifred, is cheating on him with an American named Jack Mortimer. After the concert rehearsal, he takes a taxi to the train station, sees Mortimer and shoots him at an intersection from the backseat of his taxi. The shot is not heard during the traffic noise. The taxi driver, Sponer, sitting in his car with the now-dead Mortimer, goes into a panic.