A tip from an informant led investigators to the apartment, and Duckett was known to have family in the area as well as "some criminal associations" there, according to John Cuff, chief of the U.S. Marshals Investigative Service Division.
Duckett, who was wearing a New York Yankees baseball cap when he was arrested in the first-floor apartment shortly before noon, "was trying to disguise himself the best he could," said Newark Police Detective Rasheen Peppers, who took part in the arrest.
Duckett was being held in New York on $1 million bail pending extradition. It was not immediately clear if he had retained an attorney.
He is charged with murder and weapons offenses in the death of Monica Paul, 31, on June 26.
Authorities have said Duckett shot Paul while Paul was in a waiting area by the YMCA pool where their 4-year-old son was swimming. Duckett approached and shot her several times in front of their 11-year-old daughter, authorities said.
Duckett was under a restraining order that specified no contact with Paul but allowed him to have visitation rights with their two children.
The couple had separated in August, and Paul obtained a temporary restraining order in October. It was made final later that month, according to prosecutors.
"This was a horrific act that shook the foundation of a very calm neighborhood where people live and work together," Essex County Prosecutor Paula Dow said Tuesday.
Duckett fled in a white Jeep with another man, and the vehicle was later found in Orange, where Duckett lived. Dow said Tuesday that investigators were still searching for the second man, but added that authorities don't believe he was involved in the shooting.
Cuff did not say whether the gun used in the shooting was recovered.
