The attorney for a teenager accused of fatally stabbing one classmate and wounding another in the Bronx in September says there is video, seen above, proves his client acted in self-defense.

The video is only nine seconds long. According to the attorney for Abel Cedeño, the video was recorded on a cellphone by another student who was inside the third period history class at the Urban Assembly School for Wildlife Conservation last September.

The attorney said it captures the moments before the 18-year-old allegedly fatally wounded Matthew McCree, 15, and injured Ariane Laboy, 16, with a knife.

What you can see in the video, according to defense attorney Robert Feldman, is Cedeño wearing a pink shirt in the background. The video shows another person, who is wearing a white t-shirt, who appears to be in an altercation with Cedeño. That person, according to Feldman, is McCree.

There is also another male who appears towards the end of the video who Feldman said also attacked Cedeño and is identified by the attorney as Laboy, who was critically injured in the altercation.

I spoke with Cedeño's attorney via Skype to find out what this piece of evidence means for his client.

"We are very lucky that somebody took this video because it — to answer your question — it definitely helps us," Feldman said. "If we didn't have the video, it would be an even more uphill battle to climb."

"If the district attorney herself has studied this tape, she should dismiss the case," Feldman continued.

Feldman said he did not get the video from Bronx District Attorney Darcel Clark until Thursday, during the most recent court hearing for Cedeño. Feldman said this was despite the district attorney's responsibility to turn over this type of evidence.

Cedeño is out on bail, charged with manslaughter in the case for allegedly stabbing McCree during the fight. He is also accused of assault for critically wounding Laboy using the same three-inch knife. Feldman said the video proves the defense's narrative of what happened.

"After Abel is attacked by McCree, apparently — we know from Abel's testimony in the grand jury that he was hit by McCree — hit hard — and, in self-defense to preserve his life, he stabbed Mr. McCree," Feldman said.

Up until this point, Cedeño's attorney has said the teen acted in self-defense but said he endured years of bullying and intimidation and claimed the victims were throwing pencils and paper at Cedeño before he allegedly stabbed the two teens. Feldman adds they also have evidence that McCree had ties to a local gang. McCree's family has always denied both of those claims.

"I'm not trying to demonize him. I'm sure he was a very good kid, as his mother says. However, legally if Abel knew — and he did know, because he told us that Matthew McCree was a gang member — legally his defense — his affirmative justification of self-defense is made even more crystal clear," Feldman said.

NY1 reached out to Clark for comment on the cellphone video, as well as the accusation from Cedeño's attorney that the district attorney's office did not turn the video over initially when it should have. We were told that the district attorney is not commenting because the case is still pending.