My money is on the maid, who was in collaboration with the gardener, who was really her husband. He had left them everything in his will as they were the closest people to him, and had looked after him in his last years. However they realised he was about to change his will to benefit Ms Goldigger.
Anyway who commits suicide by shooting themselves in the head twice, or did he miss the first time? (two shells) Hey, 91 years old, we should be so lucky!