The man accused of carrying out an “unprovoked, unwarranted, vicious attack” that left an 18-year-old woman dead and her sister injured was arrested Monday night on a warrant for her killing, bringing an end to a day-long manhunt, Bay Area Rapid Transit officials said.

The search for John Lee Cowell, a 27-year-old paroled felon, began late Sunday after he allegedly stabbed Nia Wilson and 26-year-old Lahtifa Wilson with a knife while the sisters were transferring trains at the MacArthur BART station in Oakland, Calif., BART Police Chief Carlos Rojas said at a news conference Monday afternoon.

Both sisters were stabbed in the neck, and Nia died from her injuries, Rojas said.

“It was, in my close to 30 years of police experience, probably one of the most vicious attacks that I’ve seen,” he said.

According to a statement from BART, an anonymous tip from a BART passenger led to Cowell’s arrest. Cowell was spotted aboard another BART train miles away from the station where the stabbing took place, the statement said. He was taken into custody without incident. He has not commented.

Cowell was recently paroled after serving time for second-degree robbery, KRON 4 reported. Alameda County court records also show several misdemeanors on his record related to vandalism, petty theft and possession of a controlled substance. Rojas said Cowell is a transient and called him a “violent felon.”

It all began Sunday night when Nia Wilson and her sisters did something they normally didn’t do.

They decided to take a BART train home from a family gathering, Lahtifa Wilson told ABC 7.

When the sisters got off their train at the MacArthur station, they became the victims of what Oakland Mayor Libby Schaaf has denounced as a “senseless act of violence.”

“All of a sudden, we transfer, just to get blindsided by a maniac,” Lahtifa Wilson said Monday, a thick bandage covering the side of her neck. “She just yelled my name, ‘Tifa, Tifa, Tifa,’ and I said, ‘I got you baby, I got you.’ ”

Lahtifa Wilson said she looked back and saw the attacker standing on the platform’s stairs, staring at them and “wiping off his knife.”

Then, Wilson said she turned her attention back to her sister, applying pressure to Nia’s neck using a baby blanket given to her by another person at the station. Two BART officers were also at the station at the time of the stabbing, and it took them “maybe a minute” to reach the platform, Rojas said.

But the attacker had already fled the scene.

“It’s more reminiscent of a prison yard assault,” Rojas said. “They do their attack so quickly that before anybody can really react, the person takes off running.”

Rojas said police found the murder weapon at a nearby construction site. He added that surveillance video also showed the attacker taking off his clothing in a BART parking structure after the stabbing.

Audio of dispatchers recorded by Broadcastify and obtained by the East Bay Times reflected the attack’s chaotic aftermath.

“We have two subjects with two lacerations,” a man says over loud background noise and people yelling. ” . . . I got another one with a laceration to the neck. We have two victims.”

“The suspect has fled the scene. Do we have a description?” another voice asks.

“Negative. All we know now is a white male. That’s all we got so far,” a man responds. “White male with red hair,” he reports as a woman interrupts saying, “No, blond hair, blond hair.”

On social media, news of the attack quickly sparked outrage, with many calling the stabbing a hate crime. The Wilson sisters are African American, and Cowell is white. By Monday night, Nia Wilson’s name was a trending hashtag on Twitter.

Others, including Grammy-nominated R&B singer and Oakland native Kehlani, labeled the attacker a “white supremacist.”

However, during the Monday afternoon news conference, Rojas said police had not yet determined a motive.

“Up to this point, we do not have any information that suggests it is race-motivated, but we cannot discount it at this time,” he said.

At the same conference, Daryle Allums, Nia Wilson’s godfather, asked the African American community to “stand down.” Allums is also a leader of Oakland’s Stop Killing Our Kids Movement.

“We don’t know if it was racist, we don’t know if it was random, we don’t know what it was,” Allums said. “Let’s get this information to find out what really happened. Let’s find out the right facts, so then we’re able to deal with this situation.”

He added: “We need your help. We don’t need us to break down right now and act crazy, tear up our city, or do anything that’s crazy right now.”

Following Cowell’s arrest, Rojas told reporters that police had still not been able to connect him with “any type of radical group or white-supremacist group.”

In a statement, Schaaf said it was important to acknowledge the crime’s context.

“Although investigators currently have no evidence to conclude that this tragedy was racially motivated or that the suspect was affiliated with any hate groups, the fact that his victims were both young African American women stirs deep pain and palpable fear in all of us who acknowledge the reality that our country still suffers from a tragic and deeply racist history,” she said.

A vigil held at the MacArthur station Monday evening turned into a demonstration as more than 1,000 people marched through the streets chanting, “No justice, no peace,” and carrying signs bearing Nia Wilson’s name, KPIX 5 reported.

Aside from reigniting fears over hate crimes, the attack also raised concerns about safety for BART passengers. Nia’s slaying was the third BART-related death in a week, Rojas said.

On Wednesday, Gerald Bisbee, a 51-year-old Pittsburg, Calif., resident, was assaulted after getting into a verbal argument with 20-year-old Abdul Bey. Rojas said Bisbee sustained a bloody lip and a small cut, less than one-eighth of an inch, to the back of his knee. Bisbee was found dead in his Pittsburg home Friday, and an autopsy determined he had died from an infection stemming from the cut on his knee, Rojas said.

A day before the Wilson sisters were stabbed, Don Stevens, 47, was “cold-clocked” on the side of his head by an unidentified man after he got into an argument with another person on the train, Rojas said. Stevens died Sunday after being taken off life support.

“This is really an anomaly,” Rojas said. “This doesn’t happen on BART. It’s rare that we have a homicide, so, of course, this is ramped up to the highest priority when you have three deaths.”

All Nia’s father, Ansar Mohammed, wants is justice for his daughter, he told ABC 7.

“I never imagined myself going through nothing like this,” Mohammed said. “This is a parent’s worst nightmare.”

More from Morning Mix: