Florida investigators say robbery may have been one of the motives in the murder of a husband and wife who had a passion for helping disabled children.

Three men have been arrested in the killing of Byrd and Melanie Billings of Pensacola, Fla., last Thursday.  Police say Wayne Coldiron turned himself in Sunday. Later in the day, police also arrested Leonard P. Gonzalez Jr. and his father.

Even with the arrests, officials said the crime seemed to have "numerous motives" and could have involved as many as eight people.

"Mr. Billings was well-to-do. He was an entrepreneur and he opened his home to the community," explained Sheriff David Morgan.

Authorities say more arrests are expected and more charges could be added for those already in custody.

The Billings had 16 children, 12 of them adopted. The children who were there during the killings, ages 8 to 14, were interviewed by police and are now staying with other family members.

The couple married 18 years ago and each had two children from previous marriages. They eventually started adopting children with developmental disabilities and other problems.

They were killed in their spacious, nine-bedroom home in a rural area west of Pensacola near the Alabama state line.

The house had an extensive surveillance system that authorities said captured the break-in.