A District postal carrier has been arrested after residents and investigators said they witnessed him tear through mail and discard boxes and envelopes at area trash bins.

Federal agents began to investigate Ronald C. Pretlow in the spring after residents in the Petworth and Brightwood neighborhoods in Northwest Washington complained about missing packages and greeting cards. Most of the residents lived on the delivery route of the 48-year-old Pretlow, prosecutors said.

One unidentified witness claimed to have watched Pretlow open numerous mail items inside his parked U.S. Postal Service vehicle, then toss mail and packages into a trash can, charging documents said. The witness wrote down the vehicle number, which belonged to the vehicle Pretlow used that day.

To test their suspicions, federal postal agents placed "test letters" into Pretlow's mail for delivery.

Two test letters contained Target store gift cards, and were addressed to separate addresses that did not exist on Pretlow's route. That meant he was required to return the letters to the post office.

The letters were never returned, investigators said, and three days later the two gift cards were redeemed by two females at a Target store.

On Sept. 12, investigators placed another "test letter" that contained an electronic-tracking device that would emit a beep on the investigator's monitor as long as the surveillance team was within a block distance. If the money was removed from the envelope, the device would begin beeping rapidly.

On his way out of the post office station, Pretlow stopped to pick up three "return to sender" bin packages, documents said.

Special agents kept surveillance on Pretlow during his postal route, and said they watched as the letter carrier dropped a black trash bag containing rifled mail and opened packages.

At the end of his route, Pretlow returned to the station, to return his postal vehicle and outgoing mail. During this time, the tracking received continued to slowly beep, indicating that test envelope had not been opened.

Pretlow then got into his personal car with the "test letter" still in his possession and drove away, documents said.

The next morning, last Thursday, authorities arrested Pretlow at work, and recovered the money that had been placed in the test envelope, documents said.

He was charged with mail theft, a crime that carries a maximum penalty of five years behind bars.