SPARKS, Nev. – He was dressed like any other student at Sparks Middle School: standard khaki pants and a Sparks sweatshirt. He was tall for a middle schooler, with dark, spiked hair, and he held a Ruger 9 mm semi-automatic handgun in his hand.

The 12-year-old boy pointed the weapon at about 30 terrified students huddled in a corner near an outdoor school basketball court early Monday. He locked eyes with eighth-grader Omar Lopez, who was nearby.

“You guys ruined my life, so I’m going to ruin yours,” he told the group, Omar said.

The gunman fired – not at the students but at a window, shattering the glass with two quick shots, witnesses said. He moved on, but he had already shot and killed a popular math teacher and wounded a student.

The boy shot and wounded another student before shooting himself fatally in the head, police said.

On Tuesday, students, parents and police struggled to comprehend the motives of the shooter, whom police declined to identify. The boy apparently believed he had been bullied or taunted, according to students interviewed here, but police said they could not confirm that.

When he said his life had been ruined, Omar said, “He looked like he was going to cry. He said it in an angry and crying voice.”

A tearful girl who said she was a friend of the shooter said she’d seen the bullying.

“Once I saw people push him in the hallway,” said Margielle Stewart, an eighth-grader who came to a makeshift memorial for the teacher at the middle school Tuesday night.

The shooter “was really nice,” she said. “He would always make a smile on your face.”

But four students interviewed earlier described a harrowing scene Monday as the gunman ordered everyone to be quiet.

“He aims the gun at us and says, ‘You guys talking, you guys talking,”“ said Antonio Ochoa, an eighth-grader.

Several students shouted, “No, no, we’re not talking. We’re being quiet,” Antonio said.

The students were trapped; they could not escape without crossing in front of the pointed gun.

“I was like, ‘Please, don’t,”“ said Adrian Aguilera, an eighth-grader. “I felt like that was the last breath I would take.”

“I thought he was going to kill me,” Omar recalled. “Because when he said, ‘I’ll ruin yours,’ in my mind, that ran through my head and I thought, oh, by ruining my life he was just going to kill me.”

Moments earlier, Antonio was 10 to 20 feet from the gunman when Michael Landsberry, 45, the math teacher some students had nicknamed “Batman” for his love of the comic book character, raised his hands and tried to block the shooter’s path.

“Mr. Landsberry, he came running up to the kid and he said, ‘Put the gun down.’ And by then I started running, and behind me I heard another shot,” Antonio said.

Mike Mieras, chief of police of the Washoe County School District, told reporters Tuesday that Landsberry was shot in the chest after the first student had been wounded.

“Mr. Landsberry calmly walked toward the shooter, putting his hands up in a motion to try to stop the individual’s actions,” Mieras said. “Mr. Landsberry’s heroic actions, by stepping toward the shooter, allowed time for other students on that playground area to flee.”

Lansberry had served in the Marine Corps, including two tours of duty in Afghanistan, and in the Nevada National Guard.

“A person like Mr. Landsberry cannot be replaced,” school Superintendent Pedro Martinez said. “He was a beloved teacher and father, a great role model, and an even better person. He will not be forgotten. He is truly a hero.”

Martinez added: “This is the action of one student. Let’s not forget it’s a tragedy for that family as well.”

Sparks Deputy Police Chief Tom Miller said police were withholding the shooter’s identity “out of respect” for his family, who are cooperating with police.

Police said that the crime scene has expanded to include the shooter’s home, where he got the gun, and that there is a possibility his parents could face charges relating to the weapon. It is illegal in Nevada to knowingly allow access to a firearm to a child under 18, unless the child is accompanied by a parent, guardian or authorized adult, according to the website of the Law Center to Prevent Gun Violence.

Police emphasized that all shots fired Monday were outside the school and that the gunman never went inside. They said pre-school safety procedures were in place, which kept some doors closed and prevented the shooter from entering crowded hallways. Police did not fire their weapons, authorities said.

Miller declined to answer questions about possible bullying of the shooter and said police did not know whether specific students were targeted.

“Everybody wants to know why. That’s the big question,” Miller said. “The answer is, we don’t know right now. We are proactively trying to determine why.”

The two wounded boys, both 12, are “stable and recovering,” Miller said. The gunman shot one boy in the shoulder and the other in the abdomen shortly after arriving on school grounds about 7:15 a.m.

Jose Cazares, an eighth-grader, said the gunman pointed the handgun at Jose’s chest on the basketball court, “like he was going to shoot me.”

“So then I turned around. I ran,” Jose said. “He shot. I looked at my chest like he shot me and then when I looked back, he shot a kid …”

Jose was not hurt. He joined the students cowering in the corner. The gunman approached and said: “If you say anything, I’m going to shoot you.”

A friend was clutching his trumpet case and praying, Jose said. The friend pleaded, “Don’t shoot, don’t shoot,” Jose said.

After the gunman shot the windows and walked away, Jose borrowed a cell phone to call his mother, Marisela Cazares.

“It was just awesome to hear his voice,” she said.

The 911 tapes released by the Sparks Police Department Tuesday reveal a deluge of calls from adults and children _ one young voice is almost breathless _ in the minutes after the gunman opened fire.

“Hi, this is Pam,” one caller told the dispatch operator. “I’m calling from Sparks Middle School. We have a shooting at our school.”

“You have a shooting?” the dispatcher asked.

“We have a teacher down,” the caller said.

Another caller, out of breath, told the 911 operator that “somebody brought a gun to school that shot a teacher.” A moment later, the caller reported: “They shot again.”

Another caller requested an ambulance. “I’ve got a kid down that’s been shot,” he said.