Solution to the "Three Scared Zombies" Kids' Mystery

Cassandra stated that her pumpkin was in the large flower bed on their front yard. She had weeded and watered the soil earlier so her pumpkin would stand out. This would make the ground around the smashed pumpkin muddy. Her brother figured out that it was best to let the suspect(s) walk away so that he could have a look at the soles of their shoes.

The drawing clearly shows only one set of footprints in the flower bed. As they walked away from the house, her brother could see which one had mud on his shoes.