When he heard gunfire erupt at Robb Elementary School, Arnfulo Reyes told his students to climb under their desks and pretend they were asleep. 

But in an interview with ABC News that aired Tuesday, the fourth-grade teacher, who was wounded in the attack, says he now believes those instructions “set them up to be like ducks.”

All 11 children who were in Reyes’ classroom May 24 were killed by an 18-year-old gunman with AR-15-style rifle. In all, 21 people — 19 children and two teachers — died.

“The kids started asking out loud, ‘Mr. Reyes, what is going on?’” Reyes said. “And I said, ‘I don't know what's going on, but let's go ahead and get under the table. Get under the table and act like you're asleep.’ As they were doing that and I was gathering them under the table and told them to act like they were going to sleep is about the time when I turned around and saw him standing there.”

Reyes was shot twice — one bullet hitting him in the arm and lung, another in the back — but he survived. He’s undergone multiple surgeries since and is scheduled for another Tuesday. 

After he fell to the ground, Reyes said he thought to himself: “I told my kids to act like they're asleep, so I'm going to act like I'm asleep also. And I pray that I hear none of my students talk.”

Reyes taught in Room 111, one of the two rooms with adjoining doors in which the shooter barricaded himself along with the children and teachers. Police quickly arrived on the scene but didn’t attempt to enter the classrooms until one hour and 17 minutes after the gunman had, despite several 911 calls placed from inside the classroom.

“One of the students from the next-door classroom was saying, ‘Officer, were in here! We're in here!’” Reyes said. “But they (the police) had already left. And then he got up from behind my desk, and he walked over there, and he shot over there again.”

Border Patrol tactical agents eventually killed the gunman.

Asked if he felt abandoned by police that day, Reyes said, “Absolutely.”

“After everything, I get more angry because you have a bulletproof vests. I had nothing. I had nothing,” he said. “You’re supposed to protect and serve. There is no excuse for their actions. And I will never forgive them.”

Fighting back tears, Reyes said he wants the parents of his slain students to know “I tried my best with what I was told to do. Please don’t be angry with me.”

Reyes said no amount of training could have prepared the teachers and students for such an attack.

“It all happened too fast,” he said. “Training, no training, all kinds of training — nothing gets you ready for this.

“You can give us all the training you want, but the laws have to change. It won’t never change unless they change the laws.”

Reyes said he doesn’t think he’ll ever be able to teach in a classroom again, but he vowed to fight for change in honor of those killed.

“The only thing that I know that I will not let these children and my co-workers die in vain. I will not,” he said. “I will go anywhere, to the end of the world to not let my students die in vain. They didn’t deserve this. Nobody in the world deserves this kind of pain. No mother, nobody deserves this. I will go to the end of the world to make sure things get changed.”