Family man and former Marine Randy Stone was a pillar in his community of Independence, Missouri.

Stone owned an insurance business, where his wife of 19 years, Teresa Stone, also worked with him. Randy and Teresa had known each other since childhood, but lost touch after Randy enlisted in the Marines at 18. The two married when Randy returned from service.

"He worshipped Teresa, she meant everything to him," Robert Davis, Randy's good friend and fellow insurance agent, told ABC News' "20/20." "We couldn't be at any sort of an event, away from work, without him constantly calling her, ...or Teresa calling him."

The couple had two children, Michael and Miranda, who were baptized at the church Randy and Teresa were married at: New Hope Baptist Church, in Independence, Mo.

"Randy was... there every ...Sunday night, Wednesday night, and if there was an activity...he was there," Randy's mother, Clara Stone Koehler told "20/20." Randy drove church buses, advised the church on financial matters, and taught Sunday school, and Teresa sang in the choir and helped in the kitchen.

New Hope Baptist's Pastor David Love was even Randy's best friend and spiritual advisor. With family, church and a tight-knit circle of friends it seemed Randy and Teresa were leading a righteous, pure, even devout life.

"He told me he would love her until the day he died, and believe me, he did," Koehler said.

On March 31, 2010, Randy, 42, was found shot and killed in his insurance office. Police investigators found no sign of struggle, and cash had been left on his desk. They quickly came to believe this was not a robbery, but a homicide.

Hundreds turned up for Randy's funeral, listening to Randy's pastor, David Love, give a stirring, heartfelt eulogy.

"We weep not just because of the separation of our loved one but because of the questions that death brings," Love can be heard saying during a police recording of his eulogy for Randy. "Questions like why, why him? Why now?"

Detectives were among the mourners at Randy's funeral, recording in the church because they believed the killer might also be in attendance.

They also found evidence that they hoped would point to the killer.

"One of our people went through … a trash canister next to Teresa Stone's office desk, and there was ... a one-page letter that had been torn up in multiple pieces," Detective Keith Rosewaren told "20/20."

The letter appeared to detectives as a happy birthday or love letter, with phrase such as, "Happy Birthday Love. I am not in control of things yet but when we are fully together your birthday will always be exciting." Police determined that the letter was written in handwriting that was different from Randy's writing samples.

When police brought Teresa in for questioning at their station, she gave officers a well-documented alibi, complete with exact times and receipts.

"No one who wasn't preparing for that, would be able to recite their whereabouts down to the minute… the way Teresa Stone did," Molly Hastings, David Love's attorney told "20/20."

However, when detectives asked Teresa about the torn up note they found in her trashcan, she didn't have an answer.

Police left Teresa alone in the interrogation room, where their camera recorded her saying, "Oh great. I forgot about that."

When police returned, Teresa explained that the note was from a secret admirer, but detectives were already suspicious.

Randy's friend and insurance agent, Robert Davis, remembered Teresa visiting him after Randy's murder, and asking about Randy's life insurance policy. "She wanted to know how long it would take for, for money to be paid out," Davis said.

Davis found it odd: "It wasn't even 24 hours after Randy had been killed," he said.

Teresa also went out of her way to establish an alibi to her friend, Pastor David Trump, when she called him to tell him about Randy's murder. "During the conversation ...after we talked about that just for a few moments, she switched, and begun to ask about my wife and my daughter," Trump recalled to "20/20."

He later called his friend Pastor David Love to confirm that Randy was dead, who Trump says also gave him a detailed account of what he'd done that day.

Police were curious why both Teresa and Love had alibis, and learned of rumors of an affair between the pair.

In their investigation, police learned that Teresa had miscarried a baby, after Randy had already had a vasectomy. Randy's Glock handgun, which matched the shell casing found at the murder scene, was also missing when police searched his home.

Based on circumstantial evidence, police had a theory that Teresa had been having an affair with Pastor Love and then gave Love access to her husband's gun so he could kill him. They needed Teresa to go on the record about the affair, the gun and the murder plot.

After detectives pressed her more in another interrogation, Teresa said, "Yes we had sex," revealing that she and Love had been involved in a decade-long affair.

She finally gave up her lover, and said that "Brother Love" had told her Randy had been shot.

Soon detectives had Love in interrogation where he did not offer much. In another room, Teresa implicated Love in her husband's murder.

"He said he walked in the office and he just aimed and he didn't look," Teresa said on a police recording.

Police obtained a search warrant and found evidence on Love's computer of pictures and emails Love sent to Teresa about starting a life together. Eight months after Randy Stone was murdered, police took Pastor Love into custody.

In November 2011, Love took a plea deal of second-degree murder. He is currently serving a life sentence and can be eligible for parole in 2036.

Teresa, indicted for conspiracy to commit murder, took a plea deal to have charges reduced, and had to acknowledge her role in the crime. She was sentenced to eight years in prison.

Both broken, the Love and Stone families are trying their best to move forward. Randy's mother Clara is still a member of the New Hope Baptist Church, and is raising money to create a memorial at the church in honor of her son. The church has a new pastor that the community has embraced and together they're hoping to make new memories, no longer defined by Pastor Love's mistakes.

Kim Love has divorced her husband Pastor David Love and recently remarried. She and her three children told "20/20" that they hold no animosity towards David or Teresa. "We have, by God's grace, been able to move forward with our lives."

Both Teresa and David declined to comment, but authorities told "20/20" David Love is ministering from behind bars, leading large bible studies in prison.

For more information on donating to the memorial for Randy Stone please visit:http://gogetfunding.com/project/memorial-pavilion#/projects_details