Heartbroken father demands justice after double stabbing at Oakland BART station

OAKLAND, Calif. (KGO) -- A Bay Area dad is pleading for justice after his youngest daughter was randomly stabbed and killed at the MacArthur BART station on Sunday night.

VIDEO: 'Remember Her' A tribute to Nia Wilson

Nia Wilson was just 18 years old when she was killed in an unprovoked stabbing at MacArthur BART station in Oakland. Fighting through sorrow, her friends, family, and the community at large are mourning the teenager who brightened the lives of those she knew, and has inspired many who never got the chance.

Ansar Mohammed is mourning the loss of his 18-year-old daughter while praying for the recovery of another.

The heartbroken dad says he never imagined going through something like this and called the stabbing a parent's worst nightmare.

"That's my baby girl up there. I want justice for my daughter," said the father.

RELATED: Here's how you can help the family of BART stabbing victim Nia Wilson

His daughter, Nia Wilson, was fatally stabbed in the neck by an apparent random stranger as she exited a BART train shortly after it arrived at the MacArthur station in Oakland.

Wilson's sister was also stabbed but survived the ordeal, she is recovering in a hospital.

VIDEO: Oakland BART stabbing victim recalls horrific attack that killed sister

Letifah Wilson spoke to ABC7 News about a brutal attack in which BART police say John Cowell stabbed both her and her sister at the MacArthur BART Station.

BART officials say the incident occurred about 9:45pm on Sunday, the station was immediately closed for the police investigation .

The suspect, identified as 27-year-old John Cowell, took off running.

"They are searching for a suspect who's described as a white male in his 20s or 30s, heavy build, and short hair. The suspect fled from the train and down into the concourse level of the station and left the station," said BART spokesperson Jim Allison.

Construction workers confirmed that BART police recovered a knife Monday morning at a construction site adjacent to the station.

VIDEO: What we know about the deadly Oakland BART stabbing

Here's everything we know about the attack that claimed the life of 18-year-old Nia Wilson.

BART says it's reviewing surveillance camera footage of the incident. Any witnesses with information are encouraged to call BART police.

The motive for the brutal crime isn't known.

Her father says Nia Wilson had attended Oakland High School.

BART officials say two young women, believed to be sisters, we're getting off the train at the station when they were attacked by a man with a knife. One woman was stabbed in the neck, she died. The other woman was badly wounded. The suspect took off running.

Go here for full coverage on the stabbing at Oakland's MacArthur BART station that took the life of 18-year-old Nia Wilson.

CONTINUING COVERAGE ON DEADLY BART STABBING:

• What we know about deadly stabbing at Oakland's MacArthur BART station
• 'Remember Her' A tribute to Nia Wilson
• Here's how you can help the family of BART stabbing victim Nia Wilson
• Chilling dispatch call describes terrifying fatal MacArthur BART stabbing
• 'He was wiping off his knife': BART stabbing victim recalls horrific attack that killed sister
• Heartbroken father demands justice after daughter stabbed at BART station
• 'Stand down': BART stabbing victim's godfather makes plea to black community
• TIPS: How to stay safe on BART
• Bart releases info on pair of homicides