by Jane E. Brody

About the author: Jane Brody is a nationally syndicated columnist who writes about personal health issues.

In 1995, a young Las Vegas family was shattered by a 3-year-old girl who found her father’s loaded revolver in a desk drawer. Thinking the gun was a toy, she aimed it at her pregnant mother, who was asleep on the sofa, and pulled the trigger. The mother died on her way to the hospital.

In 1997, a 13-year-old Brooklyn boy, whom a neighbor described as a good person who “always did the right thing,” was shot and killed while he and his friends were playing with a gun.

In Montgomery, Ala., a 9-year-old boy accidentally shot his 7-year-old brother with a gun he had found in the glove compartment of the...