JACKSONVILLE, Fla. -- A man accused of going to great lengths to spy on one of his employees has been arrested.

The man's employee told police she and the man, her boss, had an affair and when she broke it off, he resorted to high-tech stalking.

Jack Garrison, 35, is charged with aggravated stalking of a woman and her husband.

Investigators said he used two separate Global Positioning Systems, placed on each of the couple's cars to keep track of them.

Authorities said Garrison would go online and watch the couple's movements through a Web site.

"This was a bad case of an extramarital affair that went from bad to worse," said Jacksonville Sheriff's Office spokesman Ken Jefferson.

According to the police report, the two were having an affair for most of 2005 and Garrison had made threats against the woman and her husband, saying he would kill them both if she ever quit her job or if the woman stopped consenting to sexual activity.

When the woman quit, Garrison allegedly took a shocking step by putting a transmitter under the woman's car and her husband's car, too.

The devices remained on the vehicles for several months until a mechanic noticed the device during routine service to one of the vehicles and notified the victims.

"You see this sort of thing on television all of the time, and you don't think that in real life it's happening. I think sometimes a lot of ideas and thoughts are generated from movies," Jefferson said.

Over the course of a few months, Garrison allegedly checked the GPS tracker on the woman's car 511 times and checked her husband's car 516.

The police report also mentioned that an unknown assailant shot at the couple when they arrived home and were getting out of the car with their 3-year-old. Nobody has been linked to that shooting, and it is still being investigated.

Nobody at the company Garrison co-owns would comment on the accusations against Garrison.

He is charged with aggravated stalking, and his bond has been set at $750,000.