The noise was so loud it didn't sound like the gunfire from the movies to Marco Díaz-Muñoz -- it was more like an electrical generator blowing up. "But then there was one, there was two, there was three," the assistant Michigan State University professor told CNN of the sounds. And then a gunman stepped inside his classroom.
Díaz-Muñoz was about halfway through his Monday night class on Cuban literature when the world changed for him, his students and MSU as a whole. In minutes the welcoming, open campus community was shattered by another gunman's rampage in another school, by another mass shooting in America that killed the innocent.
Díaz-Muñoz's class was the first location targeted by the gunman, who also opened fire in the MSU student union before, authorities say, he was confronted by police and killed himself.
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"I could see this figure, and it was so horrible because when you see someone who's totally masked, you don't see their face, you don't see their hands -- it was like seeing a robot," Díaz-Muñoz said of the man who came in his classroom.
"It was like seeing something not human standing there."
Díaz-Muñoz could see it all as the man stepped a few inches through the rear door of room 114 in Berkey Hall, the teaching room he always requested. The professor was across the classroom, teaching at the front.
"I don't know how long he stood there," the professor recalled. "He shot at least 15 shots, one after the other, one after the other. Bang, bang, bang."
And then the gunman stepped back into the hallway, but Díaz-Muñoz did not know if the threat was over.
"My intuition told me he's walking down the hall and he's going to enter through the door I'm closest to" by the front of the room, he said.
"So,I threw myself at that door and I squatted and I held the door like this," he said, holding his hands clenched tight in front of his face, "so that my weight would keep it and I was putting my foot on the wall." All the time, he said, he was aware the gunman could shoot through the handle he was holding.
He told his students to kick out the windows of the ground-floor room so they could escape. The bottom panes would not break, but those above did, and some students were able to scramble out, he said.
Others did not go. "They were trying to cover the wounds (of the injured) with their hands so they didn't bleed to death," Díaz-Muñoz said. "They were heroic because they could have escaped through the windows. They stayed, helping their classmates."
It was 10, maybe 12, minutes -- each feeling like an eternity -- before Díaz-Muñoz saw police officers at his door, moved his body from its position as a barricade and let them in, allowing himself to go check on his students.
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"There was a horrendous scene. I've never seen so much blood," he said.
Some students had tried to take cover under the fixed seats of the classroom. One man in the middle of a row was calling out for help, saying he had asthma and could not breathe.
Díaz-Muñoz says he cannot handle seeing blood, always turning away if any is drawn from him for a test. In other circumstances he imagined he would simply have fainted from the sight, but this time other reactions kicked in.
Díaz-Muñoz said he started to pull one of the students out, but then stopped in case he was hurting more than helping.
He was then cleared from the room by police officers or paramedics, he said.
He learned later that two of his students, Arielle Anderson and Alexandria Verner, died. Brian Fraser was shot and killed at the student union. Díaz-Muñoz believes most or all of the injured were in his class, too.
"These two kids that died were just nice kids, serious students, both of them."
Seeing them fatally wounded in his class, in his favorite room of his favorite building on his beloved campus, haunts him. Díaz-Muñoz first arrived at MSU as a graduate student, then returned in 2008 to teach. Whenever schedules were drawn up, he always asked to be put back in room 114 of Berkey Hall. He knew how to work the tech there and loved the view through the windows towards the Broad Art Museum, he explained.
Now, the vision of young life slaughtered is top of his mind.
"This is the image I want to erase, that was just horrendous," he said.
"I don't know how to explain to you the guilt, the horror, the guilt, the pain that I felt, and I still feel," he said.
Díaz-Muñoz said he got home at about 3 a.m. on Tuesday. His wife, who had been waiting for him in a different hallway to the one believed used by the gunman, was with him. A chronic insomniac, he took medication and slept, he said.
For the rest of Tuesday, he gave himself permission not to think of anything, he said.
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"There is a part of me that feels like I want to go under the blankets and take more pills and not wake up for a while," he said. "I want to not remember these scenes and not have to go teach that class.
"But there is another part of me that feels a great need, a strong need to see my students again ...to see that they are alive, I need to see their faces." He is trying to write them a letter, but is struggling with what to say.
And he has a broader urge, too.
"Something kicked in in me that if I can do anything to stop this madness, I need to. People need to know what happened."
He adds his voice to those who want more to be done about the mental health crisis in the US, and to address gun control. And by telling his story, he hopes he can paint a picture of what happened.
"It's very different to hear in the news a statistic -- three more kids died or 12 more died -- than to see what I saw," he explained.
"I think if those senators or lawmakers saw what I saw, not just hear statistics, they would be shamed into action."
As a professor, he says he knows how to rationalize -- to argue one side and get you to believe it and then turn around and argue the other side and be just as convincing.
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He said he believes that politicians and others are rationalizing the causes and impacts of shootings to meet their own agenda when he feels the most beneficial changes in history have come from people allowing themselves to listen to their humanity.
He said he has felt the weight of what happened. "I was crying in that classroom, seeing the damage done and the pain and the horrible scenes ... especially those two girls," he said.
For now, he does want to teach again. To again be the strict but fair professor who pushes students to get as much as they can from the courses they pay for. Especially for the students in his Monday night Cuban lit class, with whom he now shares even more of a bond.
"Those kids to me are like my family now, and I want to see them," he said. "I want to help them, and I want to inspire them, and I want to teach them, and I want to help them finish the semester in as positive a note as it can be under the circumstances.
"I think I need to see them. I think they need to see me and be in a classroom and somehow build from the broken pieces something positive."
But not in that room. Not where a man who looked more like a robot stole lives and a sense of peace.
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