What are two factors that lead to Mr. Pignati's death?

When John and Lorraine first meet Mr. Pignati, his wife is dead, but he keeps himself busy by going to the zoo every day to see a baboon named Bobo. He calls Bobo his best friend. As their relationship with Mr. Pignati grows, it seems as if extended life also grows inside of the Pigman. Now the old man has Bobo and John and Lorraine to keep him from suffering complete loneliness.

Mr. Pignati suffers a heart attack in chapter ten as he is playing tag with the kids in his home one night. As a result, he winds up in the hospital to recover for a few days. In chapter 13, while the Pigman is away, John and Lorraine hold a party at his house without his permission. Norton, a mean boy from school, starts stealing things and breaking the pig collection right as Mr. Pignati returns home from the hospital. His heart is broken when he discovers that John and Lorraine did this behind his back. He forgives them, but he is devastated.

The Pigman decides to go to the zoo with John and Lorraine as a token of his forgiveness, but he discovers that Bobo has died. This seems to be the deciding factor behind the Pigman's will to live. First, his two close friends disrespect him and his home by throwing a wild party at his house, then he finds out Bobo is dead. Lorraine screams, "We murdered him," which shows that she feels guilty for the part she played by destroying his trust in the end. Therefore, the two factors that lead to Mr. Pignati's death, besides old age and a heart attack, are the wild party that John and Lorraine throw that breaks his heart and the fact that his best friend Bobo dies.