Who brought the family food, and why?

The members of the black community dropped off "enough food to bury the family", as a thank you to Atticus for his work on Tom's behalf.

The kitchen table was loaded with enough food to bury the family: hunks of salt pork, tomatoes, beans, even scuppernongs. Atticus grinned when he found a jar of pickled pigs’ knuckles. “Reckon Aunty’ll let me eat these in the diningroom?”
Calpurnia said, “This was all ‘round the back steps when I got here this morning. They—they ’preciate what you did, Mr. Finch. They—they aren’t oversteppin‘ themselves, are they?”
Atticus’s eyes filled with tears. He did not speak for a moment. “Tell them I’m very grateful,” he said. “Tell them—tell them they must never do this again. Times are too hard…”