The Des Moines Register published an interactive map Wednesday that allowed readers to identify schools in the state that do and do not have security guards.

The map was immediately criticized for providing would-be school shooters with an overview of easy targets. A Register staff member who answered the newspaper's general phone line Thursday told U.S. News that the map was live for 20 minutes before it was taken down.

The prominent Iowa newspaper had surveyed school districts and represented those with a security guard using a green dot and schools without guards using a red one. The map revealed a sea of red dots. Clicking on the dots revealed enrollment statistics and the town in which the school was located—but not the precise address.

"What they did [Wednesday] was provide a shopping list for every nut job in Iowa," local radio host Simon Conway told Fox News.

(Screenshot of Des Moines Register map, via TheBlaze.com)

A statement released by the Register reads: "After hearing concerns from a handful of readers, we immediately took down that interactive map. ... The recent Sandy Hook tragedy in Connecticut has forced all of us in the media, including the Register, to be even more thoughtful about how we approach our reporting and presentation on matters related to guns, crime, schools and student safety. We must responsibly balance the need to illuminate taxpayers and the public about school spending and security while also doing absolutely nothing that jeopardizes the safety of students and teachers."

On Dec. 14, Adam Lanza entered Sandy Hook Elementary School in Newtown, Conn., and opened fire, killing 20 students and six staff members within five minutes, according to new information reported Thursday by The Associated Press. The school did not have an armed security guard on duty.

The URL previously hosting the interactive map on the Register's website now hosts an article that reads in part, "The number of officers in Iowa schools could increase as officials ponder whether to add school resource officers in their buildings."