Robb Elementary School teacher Arnulfo Reyes is mourning the deaths of every single student in his classroom, and is especially angry at police in Uvalde for standing by while they were massacred.
The 4th grade teacher, who was shot twice, is speaking out for the first time, recounting the horrifying moment the shooter entered his class. Arnulfo says his students heard gunfire and asked him what was happening ... he was unsure at first, but told the students to get under their desks and pretend they were sleeping -- just as they'd practiced in drills.
He told ABC News' Amy Rohrbach that's when he turned and saw the shooter ... the beginning of 77 minutes of carnage. When it was over all of Arnulfo's students were dead, in addition to 8 others and two of his fellow teachers.
Make no mistake, Arnulfo feels the police abandoned his students, and he spoke directly to them, saying ... "You have a bulletproof vest, I have nothing. You are supposed to protect and serve. There is no excuse for their actions, and I will never forgive them."
He tearfully added, "I feel so bad for the parents because they lost a child, but they lost one child. I lost 11 that day, all at one time."
He is now a man on a mission, vowing to be active in the national debate about gun control and demanding new legislation.
Arnulfo says, "The only thing that I know is that I won't let these children and my co-workers die in vain. I will go to the end of the world to make sure things get changed."