An investigation into the shooting deaths last week of a Florida couple has yielded the arrest of a fourth suspect, officials say.

Escambia County, Fla., Sheriff David Morgan said Monday Gary Lamont Sumner has been arrested in the slayings of Byrd and Melanie Billings in Beulah, Fla. Investigators have said as many as eight people could have been involved, CNN reported.

Morgan told reporters Sumner was arrested during a traffic stop in Okaloosa County, Fla., when local police discovered the car he was driving matched the description of a wanted vehicle.

Surveillance cameras at the Billings' home showed five masked people storming into the house in what Morgan called "a very well-planned and methodical operation." The Billingses had been well known in the area for adopting special-needs children, and authorities told CNN that while robbery may have been a motive for the slayings, other motives may have been involved as well.

The broadcaster said Wayne Coldiron, 41; Leonard Patrick Gonzalez Jr., 35, and Leonard Patrick Gonzalez Sr., 56, have also been arrested and charged with murder in the couple's slaying.