A well-respected University of Pittsburgh Medical Centre researcher was said to have been on the verge of "very significant findings" related to the coronavirus when police say he was killed in an apparent murder-suicide.
Dr Bing Liu, 37, was alone at his home in the 200 block of Elm Court in Ross Township on Saturday afternoon when another man - identified as 46-year-old Hao Gu - allegedly entered the residence through an unlocked door and opened fire.
Liu was struck by bullets in the head, neck and torso, and died of his injuries.
His wife was not home at the time of the homicide, reported Pittsburgh Post-Gazette. The couple do not have children.
Police said Gu then returned to his car parked 100 yards away at Charlemagne Circle and turned the gun on himself.
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According to police, Liu and Gu knew each other prior to the murder-suicide, but they would not elaborate on the nature of their relationship, or speculate about a motive.
Nothing was reported missing from Liu's home, and police said there is no danger to the public, reported KDKA.
Liu was a research assistant professor in UPMC's Computational and Systems Biology Department, according to a statement released by his employer announcing his untimely death.
"Bing was on the verge of making very significant findings toward understanding the cellular mechanisms that underlie SARS-CoV-2 [Covid-19] infection and the cellular basis of the following complications," the statement read. "We will make an effort to complete what he started in an effort to pay homage to his scientific excellence."
Liu, who was a native of China, earned his bachelor's degree and PhD in computer science at the National University of Singapore, and then did his postdoctoral studies at the prestigious Carnegie Mellon University in Pittsburgh.
"Dr. Bing Liu was an outstanding researcher, who has earned the respect and appreciation of many colleagues in the field, and made unique contributions to science," the statement read.
He joined UPMC six years ago, during which time he co-authored a book and more than 30 publications, earning a reputation as a prolific researcher and well-regarded mentor to younger colleagues.
Dr Ivet Bahar, head of the Computational and Systems Biology Department, told the Post-Gazette that Liu had only recently begun researching Covid-19 and "was just starting to obtain interesting results".
Liu is survived by his wife and parents, who still live in China.