A man accused of fatally shooting five people at a Maryland newsroom is believed to have mailed a letter on the day of the rampage to a Virginia journalist he harassed for years and unsuccessfully sued, police and the journalist said Thursday.

The letter arrived Thursday at The Virginian-Pilot newspaper in Norfolk. It was the fourth such letter that police believe suspect Jarrod Ramos sent the day of last week's shooting at the Capital Gazette in Annapolis.

The letter was addressed to Eric Hartley, an editor at The Virginian-Pilot who once worked as a columnist and reporter at The Capital, Hartley told The Associated Press in an email.

Hartley said the pink greeting-card-style envelope was postmarked June 28, the day of the shooting. The return address was listed as "Anonymous Source."

Hartley said police opened the package safely in a lab and told him that it contained a CD and a greeting card. The card's pre-printed message was along the lines of, "Smile, you're on camera. It's your big day, and all eyes are on you," Hartley said.

Hartley said police did not reveal exactly what was on the CD but said there was nothing on it that was threatening.

But other letters sent by Ramos were, according to police.

One that arrived Monday for an attorney who had worked for the Annapolis newspaper stated that Ramos was going to the newsroom "with the objective of killing every person present," according to a copy of the letter provided to the AP by former publisher Tom Marquardt.

On Tuesday, prosecutor Jason Knight requested that the jail housing Ramos turn over "certified copies of all incoming or outgoing mail (front/back with envelope, delivered every two weeks)" for him.

Daniel Hudson, a spokesman with the Norfolk police, said the letter to Hartley is being turned over to the FBI.

Christina Pullen, an FBI spokeswoman, referred questions to Maryland's Anne Arundel County police, who are leading the investigation. They did not return a call seeking comment.

Police said they found Ramos hiding under a desk after the attack at The Capital and jailed him on five counts of first-degree murder.

Ramos has a well-documented history of harassing the paper's journalists.

Ramos filed a failed lawsuit against the paper in 2012, alleging that he was defamed in an article about his conviction in a criminal harassment case in 2011.

The newspaper published a story describing allegations by a woman who said Ramos harassed her online for months.

The defamation suit was thrown out as groundless, and Ramos often railed against current and former Capital staff in profanity-laced tweets.