Christina Yuna Lee's killer trailed her into her New York City apartment before allegedly butchering her with a yellow-handled knife Sunday morning, according to disturbing surveillance video and court papers.
"This monster, he hid himself down below every floor as he watched her go up," Lee's landlord Brian Chin told Fox News Digital.
The footage shows Assamad Nash, 25, sneak in behind Lee, 35, as she entered her building at about 4:20 a.m. at 111 Chrystie Street in Lower Manhattan's Chinatown.
Lee's landlord, Brian Chin, told Fox News Digital that Lee had taken an Uber home and been dropped off 50 feet from her building when Nash, who was hiding in a nearby alcove, spotted her.
"He knew exactly what he was doing," Chin said. "He fell back. He masked his sound. This monster, he hid himself down below every floor as he watched her go up."
Lee didn't notice as he followed her up to her sixth-floor apartment, according to prosecutors.
When she reached her front door, that's when Nash allegedly ambushed her, pushing his way into her apartment, a criminal complaint alleges.
Moments later, a neighbor heard Lee screaming. When cops arrived, Nash allegedly imitated the voice of a woman, said the police weren't needed, and refused to open the door.
Officers from the Emergency Services Unit took down the door and found Lee's blood-soaked body in the bathroom naked from the waist up and covered in more than 40 stab wounds.
Nash, who has an extensive criminal history, was allegedly cowering under Lee's bed with a stab wound to his torso and cuts on his hands and shoulder, the complaint says.
Lee worked as a creative producer for the music platform Splice and had moved to Manhattan less than a year prior from New Jersey.
Chin described Lee as an inspiration.
"She was a beautiful, independent, strong woman," he said.
Chin and Lee both graduated from Rutgers University and often chatted in the hallways of the building. "She was the type of person who would never want to bother me to fix anything and would always strike up a conversation and say hello," Chin said.
A makeshift memorial set up outside Lee's building was vandalized Wednesday, the New York Post reported.
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Nash, who is being held without bail, faces charges of first-degree murder, first-degree burglary and first-degree burglary as a sexually motivated felony. He's due back in court Feb. 18.