Principal Dawn Lafferty Hochsprung, killed in today's shooting at her Connecticut elementary school, recently installed a new security system to ensure student safety, says a CNN report.

According to the report: "In a letter this fall to parents at Sandy Hook Elementary School, Hochsprung said that every visitor would be required to ring the doorbell at the front entrance after the doors locked at 9:30 a.m. Staff began a visual monitoring system to determine entry. Parents and visitors then had to report directly to the main office and sign in. Parents would also be asked for photo identification if staff didn't recognize them."

The CNN report adds: "In her letter about the new security system, Hochsprung said glitches would be inevitable, and parents may have to wait to be buzzed inside the school because office staff is often busy on the phone, in the copy room or handling student concerns."