The feds are going after the man accused of fatally stabbing Ukrainian refugee Iryna Zarutska on a North Carolina train … because the suspect has just been charged with a federal crime.

President Trump‘s Justice Department announced Tuesday the suspect in the fatal Charlotte light rail stabbing, Decarlos Dejuan Brown Jr., is charged with one count of committing an act causing death on a mass transportation system.

Federal prosecutors say the fatal stabbing happened August 22 on the Lynx Blue Line light rail in Charlotte … and video shows a man in a red hoodie unfolding a knife and stabbing a woman who sat down in front of him.

The feds say the attacker in the video is Brown and the victim is Zarutska … and Trump’s said Brown is a “lunatic.”

Attorney General Pam Bondi says this was a “horrific murder” and vows the feds “will seek the maximum penalty for this unforgivable act of violence.” She says Brown “will never again see the light of day as a free man.”

FBI director Kash Patel says the bureau is helping the investigation to ensure justice is served and the perpetrator is never released from jail … calling the incident a “brutal attack” and a “disgraceful act that should never happen in America.”

The feds say cops were called at 9:55 PM August 22 for an assault on a light rail train in Charlotte … with callers indicating a woman had been stabbed by a male. They say responding officers found the victim in the rail car, and she had sustained fatal stab wounds.

The criminal complaint against Brown says a pocketknife was recovered from the scene. The feds say Brown pulled a knife from his pocket four minutes after Zarutska sat down in front of him, unfolding the blade and striking her 3 times from behind.

After the attack, the feds say Brown walked away from Zarutska and responding officers located Brown on the light rail platform and arrested him.

U.S. Attorney Russ Ferguson says, “Iryna deserves justice, and we will bring justice to her and her family.” He adds, “federal charges are necessary to protect the public and ensure confidence in our transportation systems.”