An employee died after being shot inside the Trump Taj Mahal Casino Resort, and a suspect was in custody, the casino's CEO said.
The employee, whose name was not immediately released, was a shift manager who had been with the casino since the day it opened in 1990.
"He was the loveliest human being you ever want to meet," said Mark Juliano, CEO of Trump Entertainment Resorts, which runs the casino. "He didn't have an enemy in the world."
Juliano said there did not appear to be a dispute between the victim and the shooter, whose identity also wasn't immediately disclosed.
The casino shut its table games down Wednesday evening and sent home workers assigned there.
Police said they recovered the gun used in the shooting after arresting the suspect in a parking garage.
It was the second incident involving a gunshot at the casino this year.
On Jan. 30, a suspect in a New York embezzlement case pulled a gun and threatened to kill himself in an office there, sparking an 11-hour standoff that included his accidentally firing a shot before he surrendered.
In that incident, the man, from Coram, N.Y., was being sought by New York authorities who had tracked him to the casino and were escorting him into a security office.
During questioning, the man pulled out a handgun. A police officer pushed him into a holding cell and locked the door.
The Taj Mahal is the largest of three Atlantic City casinos run by Trump Entertainment Resorts, the gambling company formerly run by Donald Trump.
Trump relinquished control of it during a 2005 bankruptcy, and in February he resigned as its chairman when bond holders rebuffed his efforts to buy it.
The casino, located on the Boardwalk, is one of the largest in Atlantic City, with 4,000 slot machines and 210 tables games. It opened a 782-room second hotel tower last September.
The Taj Mahal, along with the Trump Plaza Hotel Casino and the Trump Marina Hotel Casino, is in bankruptcy court following a February Chapter 11 filing.