Dr. Garen Wintemute, an emergency physician and director of the Violence Prevention Research Program at the University of California, Davis, is a pioneer in the study of gun violence as a public health issue. In his latest report, he argues that background checks should be required for the 40 percent of firearms sales made by private parties, rather than licensed dealers.

Two summers ago, Wyatt Whitebread drowned in corn at the age of 14. It happened on a hot July morning, while he was working at a grain handling operation in Mount Carroll, Ill. Soon after Whitebread climbed inside a storage bin to help empty it, equipment whirring nearby created a downward force, essentially turning the corn beneath the boy’s feet into quicksand.

As a warehouse worker in the Inland Empire region of Southern California, the nation’s biggest distribution hub for consumer goods, Jorge Soto handles shipments for retail giant Walmart every day.