A rich and handsome man was murdered, who killed him?

A rich and handsome man named James Leonard was murdered on a Sunday afternoon.
At the time of the murder there was:
The maid, the cook, the butler, the gardener and the wife.
Maid: I was fixing the table.
Cook: I was cooking breakfast.
Butler: I was polishing the silverware and the dishes.
Gardener: I was planting tomato seeds.
Wife: I was reading a book.
Who did it?