Uvalde gunman in school for almost 1 hour before shot dead

Nineteen children and 2 teachers were murdered on Tuesday at Robb elementary school in Uvalde, Texas.

Law enforcement authorities are being criticized for not acting quickly enough to stop the 18-year-old gunman who barricaded himself in a classroom and opened fire. Officials say it could have been anywhere from 40 minutes to one hour before the murderer was killed.

New video shows frantic parents pleading with police at the school on the day of the shooting, as officers try to keep the crowd back.

The 18-year-old gunman shot his grandmother in the head minutes before heading to the school and sent private messages to a girl he met online about his imminent attack.

His motive for killing 21 people and injuring 17 others is still unknown at this time.