James Kopp's 1987 black Chevrolet Cavalier was found Friday at Newark International Airport in New Jersey, according to Amherst police and the FBI. It had fake license plates.
It was not known how long the car had been there.
Kopp, 44, has been sought for questioning in the killing of Dr. Barnett Slepian since being named as a material witness Nov. 4. Slepian was shot Oct. 23 at his Amherst home.
Police have said Kopp is affiliated with the violent "Army of God" group.
"I would urge Mr. Kopp, if he is within the sound of my voice, that he do come in and talk with us," the FBI's Bernard Tolbert said at a news conference.
Investigators would not say what was found inside the car or whether they believe Kopp has left the country.
Authorities had said that Kopp's Cavalier was spotted in the Buffalo suburb of Amherst in the weeks before the 52-year-old Slepian was killed in his kitchen after being shot by a sniper firing a rifle from outside. Slepian had just returned home from synagogue with his wife.
Kopp is believed to have been in the Amherst-Buffalo area between Oct. 18 and 23, and working a construction job in the metropolitan New York area two days after the shooting, Tolbert said.
An international manhunt that includes federal and state authorities in the United States and Canada has focused on Kopp, who is from St. Albans, Vt.
Law enforcement officials say Kopp is not a suspect in the murder.
A grand jury in Buffalo is hearing testimony primarily from people who knew Kopp. DNA testing is being done on hairs found in the wooded area behind Slepian's house, where police believe the shooter may have stood.
Investigators believe the killing is linked to four earlier nonfatal shootings targeting doctors who provided abortion services in Canada and upstate New York.
Written by Bill Porter
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