NASSAU COUNTY, NY (PIX11) — A man punched a teen with a knife in hand and never meant to kill the victim, his lawyer said during opening arguments in court on Thursday.

Tyler Flach faces murder charges in the stabbing death of Khaseen Morris, 16. Morris was killed by a stab wound in the chest during an Oceanside brawl in 2019.

“We think the evidence is going to show exactly what we said in the opening statement which is that throwing a bunch of punches with a knife in hand, very sadly, one had pierced the heart,” Ed Sapone, Flach’s attorney, said. “This is not an intentional murder case.”

Prosecutors argued intent to kill can be an instinctual decision. They said Flach’s intentions were clear.

The deadly fight erupted after a large group of teens got out of nearby Oceanside High School, where Morris had transferred not long before his death.

Dozens were involved in the brawl, authorities said. Morris was targeted over jealousy for befriending a girl. Flach is “an associate” of the girl’s ex-boyfriend, who may have been jealous over the Morris’ friendship with the girl, according to investigators.

Another teen, 17, suffered a broken arm and swelling to his head during the brawl, police said. Others sustained minor injuries.

Keyanna Morris, the teenage victim’s sister, was in court on Thursday. She said she would stand strong and fight for her brother.

“He’s a monster, and monsters deserve to stay behind those bars,” Morris said about Flach.

Flach pleaded not guilty during his 2019 arraignment. He faces 25 years to life in prison if convicted. Flach wasn’t the only one arrested after the deadly brawl. Others were charged with second-degree gang assault.