There was a heightened security presence at a Bronx school Thursday after two students were stabbed, one fatally, by a classmate.

Mayor Bill de Blasio arrived at the school shortly after the NYPD began dropping off metal detecting wands and metal detectors outside P.S. 67.

As News 12 has reported, Abel Cedeno, 18, is accused of stabbing two classmates in the chest with a switchblade knife in a fifth-floor classroom at the Urban Assembly School for Wildlife Conservation on Wednesday, according to police.

First responders brought both victims to St. Barnabas Hospital, where 15-year-old Matthew McCree later died. Police say 16-year-old Ariane Laboy, the second victim, is at St. Barnabas Hospital. A friend told News 12 that he underwent surgery.

The three students had been arguing for several weeks prior to the incident and the attack may have come in response to bullying, according to NYPD Chief of Detectives Robert Boyce.

After the attack, police say Cedeno walked out of the classroom and surrendered the weapon to a school counselor. He was taken into custody.

Student Frankie santiago claims Cedeno grew angry when a paper ball was thrown across the room during third period and confronted McCree. Santiago says Laboy tried to intervene and wound up getting stabbed.

Education officials say this was the first deadly act of violence in a public school in 25 years.

Community peace groups held a prayer vigil after school ended Thursday.

Cedeno was arraigned Thursday on charges that include murder, attempted murder and manslaughter.