Oceanside stabbing suspect beat up teen in previous assault, court documents show

Five months before Nassau prosecutors said Tyler Flach fatally stabbed a 16-year-old boy in Oceanside, the community college student and aspiring rapper allegedly beat up a 15-year-old in Island Park, leaving the victim with a black eye and cuts, according to court documents.

“Defendant Flach punched the victim multiple times with a closed fist and continued punching him as he fell to the ground," according to a criminal complaint filed in Nassau County First District Court in Hempstead. 

The victim, according to the complaint, suffered "substantial physical pain, a black left eye, swollen right side of the mouth with cuts on the right cheek, and cuts on the left and right knee."

Flach, 18, of Greenway Road in Lido Beach, is being held without bail at the Nassau County Jail on a second-degree murder charge in Monday’s fatal stabbing of Khaseen Morris, a senior at Oceanside High School.

Prosecutors in May charged Flach with third-degree assault and endangering the welfare of a child in the April 18 assault of the 15-year-old in Island Park, according to the complaint. The assault occurred at 8:15 p.m. on Kildaire Road, the document said.

The victim's parents could not be reached for comment.

Flach’s attorney in the assault case, Steven Christiansen of Hempstead, did not respond to a message seeking comment Friday.

Following Flach’s arrest on the murder charge, Nassau Police Commissioner Patrick Ryder detailed Flach’s prior arrests, including the assault charge, which he said was part of an alleged road rage incident. Flach was arrested for the assault on May 23, according to police.

The complaint does not describe what preceded the alleged assault, other than saying that the victim told detectives that Flach approached him and spoke to him. Police would not comment Friday.

The assault case is pending, said Brendan Brosh, spokesman for Nassau District Attorney Madeline Singas. He declined to comment further.

Flach was also arrested on Sept. 8 — just eight days before the Sept. 16 deadly stabbing — in Albany and charged with criminal possession of a controlled substance. Details of the allegations in that case were not immediately available. 

According to Nassau prosecutors, Flach plunged a knife into Morris' chest Monday afternoon during a fight over a girl in the parking lot of an Oceanside strip mall — a popular hang-out spot for students from the nearby high school.

Flach pleaded not guilty to the murder charge and was ordered held without bail at his arraignment Thursday.

His attorney in the murder case, Edward Sapone of Garden City, has said Flach "strongly maintains his innocence." 

Morris was a senior at Oceanside High School.

Flach, a 2018 graduate of Long Beach High School and a student at Nassau Community College, went looking for Morris with a group of about seven others on Monday afternoon, prosecutors have said.

Authorities have said Flach’s friend — the ex-boyfriend of the girl — had sent threatening messages to Khaseen Morris, apparently under the impression that he was dating the girl. Morris' family said he walked the girl home from a party at her request and subsequently told the ex-boyfriend he wasn't dating her. Police said Morris and the girl were friends.

Also hurt in the attack was a 17-year-old — one of Morris' friends, who suffered a broken arm and swelling to the head. 

Police are still looking for the approximately seven others who they say were with Flach during the fight and stabbing. Police have said investigators have reviewed some video of the incident and talked to witnesses, but need more witnesses to come forward to provide statements and any video they may have. 

"We're also looking at the possibility of other subjects being charged," Ryder said during a Thursday news conference.

Long Beach Schools Superintendent Jennifer Gallagher in a letter to the school community Thursday acknowledged what she called "heartbreaking": that Morris "died as a result of a melee that involved teens from our Long Beach community."

Gallagher said Long Beach's homecoming events scheduled for this week were canceled in light of Morris' death.

"Holding a celebration this week seemed disrespectful," she wrote, adding: "I know our Long Beach community will continue to keep Khaseen and his family in our prayers in the days ahead. I am counting on the strength of this community to come together to help us heal the hurt, anger and sadness that caused Khaseen's death and that lingers still."

Keyanna Morris, the eldest sister of Khaseen Morris, said investigators told her that police know identities of the other alleged perpetrators and it's only a matter of time before they're arrested.

"They said they know the people," Morris said Friday. "Like they said at the press conference, they need to turn themselves in. So we're just waiting it out."

By Nicole Fuller

nicole.fuller@newsday.com@NicoleFuller

Nicole Fuller is Newsday's senior criminal justice reporter. She began working at Newsday in 2012 and previously covered local government.