NBC10 Investigators tracked down a cell phone sniffer who specifically targeted people using their cell phones on SEPTA bus routes. Not only did he admit to doing it, he thought it was a good thing.

The man, who calls himself Jonathan, told NBC10 Investigators, "I guess I'm taking the law personally, and frankly, I'm proud of it."

Jonathan said he doesn't want to hear people talking on their phones in public.

"It's still pretty annoying, and frankly, it's pretty rude," Jonathan said. Jonathan

said he was activating a cell phone jammer he bought online to block out conversations he doesn't want to hear.

"A lot of people are very loud and have no sense of privacy at all. When they feel like they're bothering me, I just screw in the antenna and turn the switch on," Jonathan said.

An NBC10 employee, whom NBC10 Investigators calls "Brooklyn," said she was horrified when she saw the man jamming passengers' cell phones while she was riding a SEPTA bus to work.

"He was clearly holding this device that looked like a walkie-talkie, with four thick antennas on it. I started watching him, and whenever someone started calling, he would press a button on the side of the device," Brooklyn said.

Brooklyn tipped off NBC10 Investigators, who went undercover and caught the phone thief with hidden cameras.

Minutes after boarding the No. 44 bus, NBC10 Investigators spotted Eric jamming a cell phone. Weeks later, they caught Eric as he got off the bus and told him cell phone jamming devices were illegal.

"From what I understand, it's more of a gray area. From what I understand, it's illegal to stop TV signals, radio signals. From what I understand, it's not illegal to jam cell phone signals under the FCC," Jonathan said.

But under federal law, it's illegal to use, possess, buy or sell a cell phone jammer. The federal government says violating the law could result in jail time and a fine of up to $16,000. Cell phone jammers are illegal for public safety reasons.

Dr. Rob D'Ovidio of Drexel University studies cell phone forensics and e-crime. D'Ovidio said some cell phone jammers can block GPS, two-way radios and even police radios if they are close enough.

"With a cell phone jammer, you can limit all types of communication tools that use radio frequencies. That has the potential to be a public safety disaster. It's a dangerous thing to cut off not only our government officials from communicating with the dispatch center, but also the public from communicating with 911," Dr. D'Ovidio said.

NBC10 Investigators asked Jonathan if he was worried about disturbing someone who was seeking emergency help.

"Certainly, if that happened on a bus, I think I would have been in that situation. Of course, I think that would have been a very different situation; I think I would have called 911 myself," Jonathan said.

SEPTA officials said they have received many complaints from 44 bus route passengers about lost phones. But SEPTA insisted that passengers are safe, adding that they have tested their system and handheld signal jammer alone are not enough.

SEPTA said all buses are equipped with panic buttons. Drivers can also alert police via digital destination signs on the front of buses. The transit authority said it has tested two-way radio communications and insisted cellphone jammers wouldn't affect it. But that didn't make Brooklyn feel any better.