Story highlights Tyson Jerome Barnette, 26, was on duty when he was killed

He was pronounced dead at the scene

Authorities are offering rewards of up to $125,000

Authorities are offering rewards totaling up to $125,000 for information about a fatal weekend shooting of a postal worker in Maryland.

Tyson Jerome Barnette, 26, was on duty when he was killed, according to the Prince George's County Police Department. Shortly before 7:30 p.m. ET Saturday, officers were called the scene, where Barnette was pronounced dead from apparent gunshot wounds.

"Our thoughts and prayers are with the letter carrier and his family during this very difficult time. We are all deeply saddened," said Fredric Rolando, president of the National Association of Letter Carriers.

"The nation's letter carriers deliver the mail in every community throughout the country. This tragic incident highlights the need in all operational decisions about how and when mail is delivered to give priority consideration to the safety of these dedicated public servants," he added.

The U.S. Postal Inspection Service is offering a reward of up to $100,000, while police are offering one of up to $25,000 for information leading to an arrest and indictment in the case. Both agencies are investigating the shooting.

It was not immediately clear what motivated the killing, which happened while Barnette was driving someone else's mail route, said Postal Inspector Frank Schissler.

He said there were no witnesses.