The Marjory Stoneman Douglas High school resource deputy on duty the day of the mass shooting took up a position outside but never went in to investigate, the Broward County Sheriff said Thursday.

During a news conference, Sheriff Scott Israel said the school resource officer, Scot Peterson, chose to resign and retire following a recommendation that he be suspended without pay for his actions during the massacre.

The Valentine's Day school shooting in Parkland, Florida left 17 students and teachers dead, the deadliest school shooting since Sandy Hook in December 2012.

Israel said video shows that Peterson was armed, in uniform and on campus at the time of the shooting.

He said Peterson is seen in the video driving up outside the building where the shooting was happening and taking up a position outside. However, he didn't enter the building to confront the shooter.

"What I saw was a deputy arrive at the west side of Building 12, take up a position, and he never went in," Israel said.

Israel also said Peterson stood outside the building during the incident for approximately four minutes.

The Sheriff said the video hasn't been released, and "we may never disclose the video, depending the prosecution and the criminal case," Israel said.

Despite Peterson's retirement, the internal investigation will continue.

Nikolas Cruz, a former Douglas High student, is charged in the deaths. Officials from the Broward Sheriff's office to the FBI have said they had received tips and calls for service about Cruz in the past few years.