District Attorney Stephen A. Zappala Jr. made the right call in deciding no charges would be filed against a woman whose 2-year-old son was killed by a pack of African painted dogs at the Pittsburgh Zoo & PPG Aquarium.

The decision not to prosecute Elizabeth Derkosh in the death of her son Maddox is more than humane. Bringing charges against her would have been unwarranted, Mr. Zappala determined, because the Nov. 4 incident was a tragic accident.

The Whitehall woman had lifted her son up on the side of a viewing platform at the wild dog exhibit where there is no protective barrier above a railing, which is about 4 feet off the ground. The DA said that, according to witnesses, Maddox unexpectedly lunged forward while in his mother's arms, which caused her to lose her hold on him. He toppled into the enclosure, where he was mauled. The witnesses said it appeared that the child, who wore glasses, believed there was glass or Plexiglass in front of him. And there should have been.

That is hardly the fault of Mrs. Derkosh, who did what countless other parents before her have done to help their children get a look at the zoo's endangered dogs.

The lack of a protective barrier is part of an investigation being conducted by the U.S. Department of Agriculture, which has jurisdiction over zoos. Pittsburgh Police and the Association of Zoos & Aquariums also are continuing their investigations, important work with the goal of preventing another tragedy and improving safety for zoo visitors.

First Published: November 30, 2012, 5:00 a.m.