ST. LOUIS • Jovica "Joshua" Petrovic was a vengeful man, federal officials said.

When his short-lived marriage began crumbling in 2009, Petrovic threatened to release family secrets.

Beginning in 2010, after his wife said she wanted a divorce, he stalked and harassed her and mailed roughly 150 homemade postcards to her boss, friends, relatives and neighbors. The cards carried suggestive pictures, insults and the address of a website where he posted still pictures from secretly made videos of them having sex, embarrassing personal information and some outright lies.

He demanded $100,000, her wedding and engagement rings and furniture he claimed she stole from a storage unit, in exchange for shutting down the site.

It was "a vile and malicious attempt to destroy (his wife's) life" and a "calculated psychological attack," Assistant U.S. Attorney John Sauer told a jurors Friday in Petrovic's trial here on federal charges.

They deliberated less than 21/2 hours before finding Petrovic guilty of four counts of cyberstalking and two counts of extortion. They found him not guilty of an interstate stalking charge that involved allegations that he had tried to run his wife off the road.

Petrovic, 61, who has a doctorate in economics and filed his own legal motions in the case, had almost no reaction to the verdicts, only wiggling his fingers and moving his lips briefly. After jurors left, he began flipping through his legal papers and evidence.

During this week's trial, Petrovic blamed much of the tumultuous relationship on his former wife. He testified that some of the threats were simply attempts to force her to talk to him or to protect himself.

"Every divorce have dark side," said Petrovic, who was born in Croatia and raised in Germany. "Every end of relationship have dark side. Some people go crazy and some people don't understand," he told the jury.

Petrovic said he began creating the website only two months after the marriage. When his attorney, Steve Stenger, asked why, Petrovic responded, "I wonder this. Why? For me. For my life. Why you create any website?"

Stenger is the fourth lawyer either hired by Petrovic or appointed to represent him.

The defendant's ex-wife, more than 20 years his junior, testified about her angst. During their marriage, he lived mostly in the Fort Myers, Fla,, area and she in various locations, mostly in St. Charles County.

In closing arguments, Stenger characterized Petrovic's threats as merely the rantings of someone upset by a break-up.

But Sauer, the prosecutor, said Petrovic was trying to destroy any support his wife may have had among friends, relatives and co-workers.

Petrovic could face more than four years in prison when sentenced Feb. 15, said Postal Inspector John Jackman, who helped investigate the case.