Four Uvalde shooting victims left classrooms alive. Investigators are reviewing whether a faster response could have saved them.

Crosses are on display on May 26 for the people killed at Robb Elementary School. (Credit: Lauren Witte/The Texas Tribune)

Investigators conducting a criminal probe into the Uvalde school shooting and subsequent law enforcement response are trying to determine whether any victims who died may have survived if police had intervened sooner.

Four victims — teacher Eva Mireles and three students — who had heartbeats when they were rescued from adjoining classrooms in Robb Elementary died that day. They had been trapped with the shooter for more than an hour.