Her 18-year-old sister Nia Wilson passed away at the scene.
"I'm her protector and I feel like I didn't protect her," said Wilson.
"She's just yelling my name, 'Tifah, Tifah, Tifah,' and I said, 'I got you baby, I got you,'" said Wilson as she described the unprovoked stabbing.
RELATED: Suspect identified in Oakland BART fatal stabbing
Wilson said she responded by telling her sister she loved her.
"We're gonna get through this, I got you, you're my baby sister," said Wilson.
In describing her sister Nia, she said, "The most sweetest person on the earth, she didn't do nothing to nobody I didn't do nothing to nobody and for this to happen is just outright crazy."
Wilson says she was with two of her sisters, including Nia, heading home from a family function. She says they never saw Cowell or exchanged words with him prior to the stabbing.
"All of a sudden we transfer just to get blindsided by a maniac, for what I don't know," said Wilson.
"I looked back and he was wiping off his knife and stood at the stairs and just looked. From then on I was caring for my sister," continued Wilson.
Wilson says a woman with a stroller that she and her sister had allowed to pass earlier gave her a baby blanket to apply pressure to her sister's neck.
Wilson says she was also hurting because Cowell had stabbed her after stabbing Nia.
She says when other BART passengers attempted to stop Cowell, he ran from the scene.
VIDEO: Heartbroken father demands justice after daughter stabbed at BART station
Describing her sister, Wilson said, "That's my heart, she was my heart, no matter our ups and downs we still come back to each other like it was nothing."
She says the family hadn't seen Nia in six months because she was with her mom's side of the family. Wilson also says they rarely took BART.
"As young black women, we shouldn't have to look behind our back you know, we should be living freely like everybody else," said Wilson.
VIDEO: 'Stand down": BART stabbing victim's godfather makes plea to black community
"He just felt upon himself to take his anger or whatever the case may be out on innocent women," Wilson continued.
Nia's nickname according to her family was PG, short for pretty girl. They say she loved to spend lots of time getting ready and doing her makeup.
Wilson says her baby sister wanted to be a lawyer or do something in criminal justice. Also that she wanted to have a dance studio and her own makeup line.
As for her own injuries, Wilson has stitches in her neck.
"Missed the artery, thank God, missed the veins, it's pretty deep and he tried to swing twice hit me in my head, so I have a knot in my head," said Wilson.
Still she's focused on Nia.
"I want justice for my sister," said Wilson.
Suspected killer of Nia Wilson arrested for MacArthur BART stabbing
Cowell was arrested Monday night. Officers say they followed up on tips from the public and found him on an Antioch-bound train.
BART Police Chief Carlos Rojas held a media availability at Rockridge Station. He says the arrest was uneventful and that the suspect was taken into custody without incident.
RELATED: This is the moment the BART stabbing suspect was arrested
A BART rider on an Antioch-bound train captured the arrest of 27-year-old John Cowell on her cellphone camera. Officers had intercepted the train at the Pleasant Hill BART station after getting tips from the public. The man, wanted for Sunday night's double stabbing, had been at large for nearly 21 hours.
"They asked him what his name was. He was truthful with the officers in terms of his name and they asked him for identification and he did provide a California identification," said Rojas.
The arrest comes as a huge relief for the Bay Area, where the random attack has triggered outrage and protest.
VIDEO: What we know about the deadly Oakland BART stabbing
"I don't know what it was but he was just always kind of a problem," said neighbor Carol Kincaid.
She has known Cowell since he was a child. She says he's lived in and out of this Concord home and over the years has been in trouble with the law. In fact, according to our media partners at the East Bay Times, Cowell has an extensive criminal record.
Kaiser Medical in Richmond filed a restraining order against him after he was accused of threatening to kill an employee in 2016.
Then he was sentenced to prison for robbery and after serving two years, was out on parole four months ago.
As to what led to Sunday night's stabbing, police still don't have a motive.
"We haven't connected him to any type of radical group or white supremacist group or anything like that," Rojas added.
Oakland Mayor Libby Schaaf released a statement on the suspect's arrest: "The senseless murder of Nia Wilson and the stabbing of her sister Latifah has traumatized our community, and most especially their family and friends. I want to again express my condolences to them, first and foremost. I am relieved to learn that the suspect was apprehended after an anonymous tip from a BART rider led to the arrest of the suspect. May this serve as the first step in bringing justice for the Wilson family, and healing to our community. As the Mayor of Oakland, it's important I acknowledge that this horrific crime has a 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. I recognize that Sunday's tragic events came on the heels of news that white supremacists were attempting to gather at a downtown bar this evening. I appreciate the commitment of these establishments to prohibit such activity in their businesses and then decided to hold a "Pro Oakland Movement" event this evening to support organizations that fight bigotry and discrimination on behalf of our community and our values. Oakland has no room for hate or white supremacy."
Murder suspect identified in MacArthur stabbing. John Cowell is considered dangerous. Please call 911 if spotted. RIP Nia Wilson. We will bring this suspect to justice. Our thoughts are with the family and friends. Details: https://t.co/DEkTJvJnNe pic.twitter.com/igZU2bdel7— SFBART (@SFBART) July 23, 2018
Ahead of tonight's vigil for BART stabbing victim Nia Wilson pic.twitter.com/N2klP0BlZQ— Melanie Woodrow (@MelanieWoodrow) July 23, 2018
Here are the 5 siblings. They tell me they hadn't seen Nia Wilson in 6 months. The family had just come back together for a family gathering. pic.twitter.com/NBJii1ramv— Melanie Woodrow (@MelanieWoodrow) July 23, 2018