How is Willy's suicide foreshadowed in the first act of Death of a Salesman?

Linda announces to the boys at the end of Act I that Willy has been in a series of car accidents, and that the accidents themselves seem like deliberate attempts to kill himself.  She also states that she recently found a rubber pipe and is concerned that Willy is considering inhaling gas to end his life.  In the end, that is what he does - inhales gas from his car.