The man was being treated at Hackensack University Medical Center.
It is not clear when he was admitted.
"Our prayers are with his family during this difficult time," Murphy said in a tweet.
The other two deaths were a Little Ferry man and a Freehold woman, whose cases were reportedly linked.
The news came hours after the City of Hackensack announced its first case: A 49-year-old woman who was self-quarantining at home.
Meanwhile, Bergen County was preparing for a shutdown as part of extreme regulations set forth in an order by County Executive Jim Tedesco.
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