(WMC) - A man accused of shooting and killing two postal workers in Henning, Tenn., has pleaded guilty to all seven counts in a federal indictment against him.

In exchange, the government agreed to dismiss its intent to seek the death penalty.

Chastain Montgomery Sr., 50, is accused of shooting and killing Paula Robinson and Judy Spray during an October 2010 robbery of the Henning post office, which netted a total of $63.

Investigators say his son, Chastain Montgomery Jr., participated in the robbery and killings too. He was shot and killed in a shootout with Tipton County deputies months later, after another bank robbery in which he was a suspect.

During a change of plea hearing, federal judge Jon McCalla asked Montgomery a series of questions. At one point, he asked Montgomery what he did on the day of the murders as family members of the victims could be heard sniffling.

"I robbed the post office and shot Paula Robinson. I robbed the credit union in Lavergne and the bank in Smyrna," Montgomery answered.

"And what happened to Mrs. Spray?"

"I killed her too."

"How?"

"I shot her with the nine millimeter."

Montgomery's attorneys, Mike Scholl and Anne Tipton then interjected and had him re-answer the question to indicate he has caused the deaths of both women.

According to the indictment, he purchased both guns used in the murders and gave his son one of them. Prosecutors say his son killed Spray.

As part of the plea agreement, Montgomery agreed to serve life in prison without the possibility of release. However, an official sentencing hearing will be held at 9 a.m. on Tuesday August 12.

Montgomery was a corrections officer in the Tennessee prison system. Prosecutors say he pulled these bank robberies and the post office murders on days he was scheduled off from work. Prosecutors say Montgomery told them he picked the post office in Henning because he once worked there as a janitor and knew there would be a lot of money in the safe.

According to prosecutors' version of facts, Montgomery and his son entered the post office on the morning of October 18, 2010, pulled out their guns, jumped on the counter, and stole $63 from Robinson's cash register.

They held both women in the back at gunpoint and tried to make them open the safe. When the safe would not open, prosecutors say Montgomery got angry and shot Robinson 5 times while his son shot Spray 4 times.