(CNN)A veteran letter carrier was shot and killed this week while delivering mail in rural South Carolina, according to the US Postal Inspection Service.
Irene Pressley delivered mail for the post office in Andrews, South Carolina, and had worked for the service for almost 22 years, said David McGinnis, the inspector in charge of the US Postal Service's Charlotte Division.
"Make no mistake, the perpetrators of this crime will face justice," McGinnis said during a Friday news conference. "Nothing we do is more important."
Jody Bouchette lives near where Pressley was found shot to death in her vehicle on her rural route Monday.
"She was a sweet lady," he told CNN affiliate WCSC on Tuesday. "She would do anything in the world."
He said he watched when authorities removed the vehicle from the scene.
"It just broke my heart. For the whole back glass to be shot out and bullet holes in the front of it and all that," he said. "I broke down and cried."
A woman on Pressley's mail route said she was very friendly.
"She would blow the horn like everybody else because we have a dog," Barbara Calhoun told CNN affiliate WPDE. "She was always real pleasant, always talked."
McGinnis said a team of 70 people is investigating Pressley's death. It includes personnel from the US Postal Inspection Service, Williamsburg County Sheriff's Office, South Carolina Law Enforcement Division and the US Attorney's Office.
Williamsburg County Sheriff Stephen Gardner said his deputies are working 12-hour shifts, but they need help. Authorities do not have a suspect.
"We can do a lot of technical things and we can do a lot of things right when it comes down to some things. But the one part that is integral that we need help and I plead to you is from our community," the sheriff said. "You have to give us information to work with."
In an online post, the postal inspection service said, "The US Postal Inspection Service is offering a reward for information leading to the arrest and conviction of the suspect(s) in the homicide of a letter carrier in Andrews SC." It didn't say the amount of the reward.
Pressley's funeral service is Saturday, according to the Henryhand Funeral Home.
Andrews is in the Lowcountry of South Carolina, about 50 miles northeast of Charleston. It has roughly 2,800 residents, according to the US Census Bureau.