In Seedfolks, why did Amir say the garden was the reason the three men chased down the person who stole a purse?

In the book, Amir explains how the community garden has brought people of all races together. During the harvest festival, everyone traded harvests and mingled freely among each other. All the barriers seemed to have been broken down because of the shared interest in the garden.

Amir provides some examples of how the community has become much closer. When someone dumped tires into the garden and crushed four rows of someone's corn crop, community growers worked together to take the tires to the curb. Then, a few weeks later, a woman screamed that a man was stealing her purse. Three men, including Amir, rushed to apprehend the thief and to hold him hostage until the police arrived. Amir contends that the garden has created a sense of community that has allowed people to feel a sense of belonging and camaraderie in the neighborhood. He admits that, until then, he had never chased down a criminal before. If the theft hadn't happened near the garden, he doubts that he and his two friends would have chased down the thief.