Nashville, Tenn. ? A man who posted false information on an online encyclopedia linking a journalist to the Kennedy assassinations says he was playing a trick on a co-worker.

Brian Chase, 38, ended up resigning from his job and apologizing to John Seigenthaler Sr., the former publisher of the Tennessean newspaper and founding editorial director of USA Today.

“I knew from the news that Mr. Seigenthaler was looking for who did it, and I did it, so I needed to let him know … that it was done as a joke that went horribly, horribly wrong,” Chase was quoted as saying in The Tennessean.

Chase said he didn’t know the free Internet encyclopedia called Wikipedia was used as a serious reference tool.

The biography he posted, which has since been replaced, falsely stated that Seigenthaler was linked to the Kennedy assassinations and had lived in the Soviet Union from 1971 to 1984.

The entry motivated Seigenthaler to write an op-ed piece for USA Today blasting Wikipedia’s credibility. He described himself as a close friend of Robert Kennedy and said he had worked with President Kennedy.