A sense of measured relief worked its way through this small town Thursday after a man was charged with shooting and killing two female postal workers, a crime that had sewn months of uncertainty and fear among locals.

Chastain Montgomery Sr., a Tennessee prison guard, was indicted by a grand jury on two counts of killing a government employee in the Oct. 18 shootings inside Henning's small red brick post office. The indictment says the 47-year-old Montgomery killed Judy Spray and Paula Robinson while robbing the post office with his son.

The charges mark the first positive news to come out of the four-month investigation of the slayings that left many of the town's 1,200 residents wondering if the killer was living among them. Authorities had been tightlipped before Thursday about a possible motive or how many people they thought were involved.

"Just knowing that they have somebody arrested is bringing relief to a lot of the townspeople, period," said Renee Jackson, a 49-year-old nurse who lives across the street from the post office from the shuttered post office that served as a hub of activity for the town about 45 miles northeast of Memphis.

The six-count indictment was announced in Memphis on Thursday. Edward Stanton, the U.S. Attorney for the Western District of Tennessee, said Montgomery and his son, Chastain Montgomery Jr., aided each other in the crime but declined to elaborate. He said the investigation is ongoing.

The 18-year-old Montgomery Jr. was killed in a shootout with police on Feb. 14 after a police chase, and his father is jailed on charges related to the shootout. Afterward, federal authorities began investigating whether a gun used by the teenager was also linked to the post office shootings.

The sheriff's office in Tipton County, just north of Memphis, said the teenager got out of a stolen pickup armed with two handguns and fired at officers several times before a deputy shot him dead.

Chastain Montgomery Sr. was arrested when he went to the scene and tried to get in the stolen pickup truck his son had been driving. He ran through crime scene tape, ignoring the shouted warnings of officers and headed straight for the truck, which was still running.

The father was jailed on charges of evidence tampering, being an accessory, theft between $1,000 and $10,000 and resisting arrest. In the newly announced indictment, he also faces federal charges of robbery with a dangerous weapon, using a firearm in a crime of violence, and two counts of unlawfully causing the death of a person.

Montgomery Sr. is in the process of being transferred into federal custody and no hearing has been set in federal court.

Before his arrest, rumors of who shot the women and why spread throughout the town as more than 100 investigators worked on the case. The U.S. Postal Inspection Service offered a reward of $50,000 for information leading to a conviction.

On Thursday, the American flag outside the closed post office remained at half-staff, while a temporary mail trailer sat yards away.

Abe Humadi, a clerk at the Midway Market and gas station in Henning, said people are still wondering why the women would be shot during a daytime robbery of a post office, which likely does not have as much cash as other nearby businesses.

Humadi, 30, said he knows people who have moved away because of the shootings. The town has experienced increased drug and crime activity in recent years, residents say.

Still, word of the charges was welcomed by Humadi, who works just steps from the post office.

"Now everybody is feeling more comfortable," he said.

The investigation has not ended, however, and a trial isn't imminent. The post office still serves as a reminder of shootings that authorities have called cold, calculated and disturbing.

"When people drive up on the parking lot, they're still going to recognize for a long, long time that murders happened here, and they're going to think about it" Jackson said. "I know I will."