Authorities now say the 18-year-old gunman who killed 21 Tuesday in Texas was not confronted by a school resource officer before he entered the building, contradicting previous police accounts. Questions are also growing around why officers were not able to stop him sooner. The shooter was inside the school for about an hour before he was killed by law enforcement. Frantic parents arriving at the scene say that they were held back by police. Building an accurate timeline is now a focus of the investigation. CNN's Shimon Prokupecz begins our reporting from Uvalde.

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