Action News has learned 22-year-old David Grier, of the 400 block of Edgemore St. in West Philadelphia, has been arrested in connection with the murder.
Johnson, a former student at Hussian School of Art, was reported missing back on the morning of November 3, 2017.
A passerby found her body face-down in the creek near the Spruce Street entrance of Cobbs Creek Park later that morning and called 911.
Philadelphia Police Capt. John Ryan said Johnson was with Grier when she was last seen, the night before her body was found.
It's not clear how long they knew each other, but police say Johnson and Grier were acquaintances.
"We observed them on public transit traveling together and again, they were last seen in each other's company," Capt. Ryan said. "She was last seen alive in his company. But that is all we are willing to talk about at this point."
Investigators believe Grier strangled Johnson before dumping her body along Cobbs Creek.
Grier, who was on parole after being charged in 2016 for attempted murder in Oakland, Calif., was taken into custody Wednesday afternoon, Ryan said.
According to an essay Johnson penned while interning at Mass Parks Student Career Intake Program, she was passionate about the arts and land conservation.
At the time of her death, the Hussian School of Art released a statement on the loss of Johnson, reading: "Ki, as she was known to all, was a honors student, on the Dean's List and an excellent artist."
Investigators did not elaborate on a motive, but say Grier is charged with murder, robbery and related offenses.
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