The passport of a fugitive Georgia professor on the run since allegedly gunning down his wife and two others was among the items found in his abandoned vehicle, the Atlanta Journal Constitution reported.

Authorities were concerned George Zinkhan, 57, would try to flee the country, but the University of Georgia professor never showed up Saturday for a Delta flight to Amsterdam he was issued a ticket for. Zinkhan owns a house and has a part-time job at Free University there.

It was not immediately clear what other items were found in the vehicle.

On Friday, authorities found his 2005 Jeep Liberty in a ravine near his home.

They theorize that Zinkhan is still in the Atlanta area — where he lives and teaches business courses — and that the rampage may have been sparked by a fight with his wife, who was reportedly planning to leave him.

"We don't believe he drove it off, 'cause it's in drive," one officer told reporters of the crashed Jeep, according to MyFOXAtlanta.com. "Looks like he put it in drive and maybe kind of pushed it off the edge."

Police hadn't previously revealed a motive, but FBI agent Greg Jones said Friday that interviews with friends and family indicate the shooting likely stemmed from a domestic dispute between Zinkhan and his wife, 47-year-old attorney Marie Bruce.

Authorities have some indication she was preparing to file for divorce, he said.

Zinkhan has been missing since last Saturday, when he allegedly fled the scene of the triple shooting murders of his wife and two other men at a community theater where the victims were members.

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He was last seen driving away in the Jeep after dropping his children off with a neighbor. The children were in the car during the shootings but weren't hurt.

Zinkhan is accused of killing Bruce and two members of her community theater group, Ben Teague, 63, and Tom Tanner, 40, in front of a theater in Athens, Ga.

Authorities across the nation and in Europe have been looking for Zinkhan since the April 25 shootings.

Zinkhan's brother has said relatives have been working to help Athens-Clarke County police and the FBI find him.

The University of Georgia is warning students to be cautious until he's found.

Before joining the faculty at the University of Georgia, Zinkhan held academic positions at the universities of Houston and Pittsburgh.

He has a doctorate from the University of Michigan and graduated from Swarthmore College in Pennsylvania in 1974.

The shooting victims were members of Town & Gown Players, which was staging a performance of "Sherlock Holmes: The Final Adventure" at the theater.

Two others were hurt by bullet fragments.

Zinkhan's wife, had been serving as Town & Gown's president after years of volunteering with the group.

Click here to more on this story from the Atlanta Journal Constitution.

Click here for more on this story from MyFOXAtlanta.com.

The Associated Press contributed to this report.