UPDATED 03/01/12 4:35 p.m.

CHICAGO (CBS) — One 17-year-old student is dead, and another is injured, after being stabbed by another student Thursday morning at a special school on the city’s Far South Side.

As CBS 2’s Susanna Song reports, the students were stabbed around 7:30 a.m. at Infinity High School, a therapeutic day school program housed in the old Oliver Goldsmith Elementary School, at 10211 S. Crandon Ave. in the South Deering neighborhood.

WBBM Newsradio’s Bernie Tafoya reports the assailant got into an argument with one of the students before they lined up to go through a security checkpoint, and one started stabbing the other. The students are screened for metal objects with wands each day, but the stabbing happened before the students were screened.

LISTEN: WBBM Newsradio’s Bernie Tafoya reports

As CBS 2’s Dana Kozlov reports, exactly what sparked the attack was still under investigation Thursday afternoon.

The two students had had a previous dispute, and already had been counseled to try and resolve their differences, a representative said for Florida-based school operator AMI Kids said.

The second student stepped in an attempt to stop the attack, and was also stabbed.

The wounded students were taken to Advocate Christ Medical Center in Oak Lawn, police said. One victim, identified by family members as Chris Wormley, later died, according to the Cook County Medical Examiner’s office.

The other student remained in serious condition at the same hospital.

Despite searching, police were not able to find the weapon used in the stabbing. The suspect was in custody, but that was small comfort to the family of the teen who died. Wormley’s brother crumbled to the ground in the parking lot outside Advocate Christ Medical Center in Oak Lawn after learning of Chris’s death.

The other students at the school were sent home for the day around 9:30 a.m. Some were bussed away.

When they return on Friday, counselors will be on hand to talk to them about what happened.

Infinity High School is a privately-operated program in the Chicago Public Schools system for students with behavioral and emotional needs, operated by AMI Kids. The company has a stated mission of “separating a troubled past from a bright future” on its Web site.

Police spent most of the day inside Infinity. A spokesperson for the parent company – AMI Kids – said before school Thursday morning, some sort of altercation took place between Wormley and the student responsible for the stabbing. A third student apparently tried to intervene and was also stabbed.

Infinity executive director Willie Tubbs said, “we have not had a previous situation of this magnitude of any kind within the community, within our school, and this is just an unfortunate matter.”

Tubbs said the stabbing happened between two sets of school doors, before security personnel would have used a wand to check for weapons. Now, all security procedures will be reviewed. Chicago Public Schools officials said they would join AMI Kids to conduct a thorough review of security.

“Anytime anything happens, I think we will have to … look at everything that we do and how we do it. So everything is on the table at this point,” Tubbs said.

About 20 students attend the school. Some, but not all, are Chicago Public Schools students.

“My parents just live right across the street, and we know the kids that go there,” said local resident Maria Freund.

“It’s so close to home,” added neighbor Edwina Jones. “It’s so crazy.”

Some parents walking their children to a nearby elementary school couldn’t believe the incident happened so close to their homes.

“It’s scary, because this neighborhood is really a good neighborhood,” said Larry Thigpen.

“Really shocking to come outside and see something like this going on,” added Angel Harris.

Meanwhile, Wormley’s family was gathered at the hospital at the time of his death. As CBS 2’s Roseanne Tellez reports, his family said he loved playing video games, and basketball; and that he was a good kid, who’d expressed concerns about violence at his school.

“He said the school is a bad school. That’s all they do is go in a fight and do stuff like that,” Wormley’s brother Davier Prince said. “He don’t do stuff like that.”

CBS 2’s Susan Carlson reports Prince was among those gathered outside Advocate Christ Thursday morning, He came to visit his brother, only to learn the devastating news that Chris didn’t make it.

Both Prince and Wormley’s cousin, Tyran Wormley, said the victim was a good kid who went to a tough school, and that Wormley became a victim because of the troubled students around him.

“He don’t do nothing; be in the house all day. He don’t gang bang. He don’t be into all that. All he does is play games, and that’s it,” Prince said.

Prince said he was asleep when the stabbing happened, but saw his brother last night. The biggest problem, Prince said, was that the school was such a troubled place.

Tyran Wormley says the school shares some blame for the fact that the stabbing happened.

“You would think that you could send your child to school without him, you know, being murdered,” added Tyran Wormley. “You know, it’s just unbelievable. … In my opinion, the school should have saw this coming. They should have recognized there was a problem. So, I blame the school as well.”

The child who had the knife was arrested, and was in police custody within less than an hour of the stabbing.