Roger Abbott collected Bibles. His wife, Dorothy, was a consummate caregiver, working as a nurse and doting on their four children.

Why anyone would kill the 82-year-old former chemical engineer and his spouse, 78, remains a mystery nearly two weeks after they were found dead in their Dunwoody home, which had been set on fire.

“This was a tragedy and we are working diligently to solve it,” Dunwoody Police Chief Billy Grogan said Monday

Police believe someone purposely ignited the residence in the late morning of July 1 to hide the double murder. However, law-enforcement officials have not said whether they have a suspect or person of interest, indicating they don’t want to compromise their investigation.

Grogan met Monday morning with members of Retired Old Men Eating Out, a monthly breakfast group that counted Roger Abbott as a member. The chief wanted to reassure people that his department was giving full attention to the investigation.

Rumors remained rampant in the upscale suburb in northern DeKalb County that the retirees were tied up before the blaze or they had been shot, or both. Police would not discuss any details of the crime.

Neighbors speculated the attack was random and feared the older couple was targeted as easy prey, especially because the Abbotts were known for being outwardly friendly.

“I just think those people were innocents, sweet and unaware of the evil at loose,” said Graham Andoe, who has lived in the Village Mill neighborhood behind the Abbotts’ Peeler Street home for 39 years.

Andoe, a member of Roger Abbott's breakfast group, said petty crime, such as car break-ins, had spilled into the neighborhood.

The Abbotts’ home is less than a half-mile from Shallowford Road, one of the city’s high-crime areas with a cluster of apartments and small shops. Andoe’s wife was a victim there three years ago, held hostage during a drug store armed robbery near the intersection of Shallowford and Peeler.

The murdered couple's two-story home had an unusual trait: the attached two-car garage came without a door, possibly providing easy access to the home. Police again would not comment.

“We are following every lead we have and looking for more,” Grogan said, dealing with the department's first murders since the department went into operation in April 2009.

Roger Abbott visited the nearby Kroger store every Wednesday because seniors were given a discount on purchases.

Dorothy Abbott devoted her life to a disabled adult son who lived at home; that son was away at a summer camp when the attacks took place.

Other family members did not return phone calls Monday. The couple’s four adult children held a memorial service last Thursday at Peachtree Presbyterian Church, where Roger and Dorothy Abbott were members for 33 years.

On Monday afternoon, a small memorial that mourners had erected on the front lawn was a bright spot for an otherwise empty house. An orange flag for Auburn University, Roger Abbott’s alma mater, flapped next to smaller American flags and several bouquets of flowers.

“I have a hard time understanding why this would happen,” said David Holland, a neighbor for 18 years. “It’s hard to make sense of it all.”