Updated

A Florida couple killed in their home had an extensive surveillance system in the house that recorded three apparently experienced criminals swiftly slip into the house before driving off in a red van, police said.

Several tips from the public led investigators to a red, 15-passenger van Saturday morning that they believe was used as the getaway vehicle by the three men, believed to be in their "late teens on up," Escambia County Sheriff David Morgan said.

Authorities were questioning two people linked to the van, but no arrests have been made.

Byrd and Melanie Billings of Beulah, a rural area west of Pensacola near the Alabama state line, were found shot dead in their home Thursday evening.

The couple, known for their large family of adopted children, had an extensive surveillance system in the house and Morgan said authorities have reviewed the tapes repeatedly.

The couple was killed as the children slept.

"I will share this with you — I think we were surprised by the rapidity of the crime," Morgan said. "It suggests experience to me."

Officials still don't know why the family was targeted, Morgan said.

The couple was well-known locally for adopting children with developmental disabilities. They owned several local businesses, including a finance company and a used car dealership.

The Billingses had 16 children, 12 of them adopted. Eight of the children, ages 8 to 14, were in the home when the couple was killed.

Investigators interviewed the children, who 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.

In a 2005 story in the Pensacola News Journal, the couple said they wanted to share their wealth with children in need, but didn't imagine their family would grow so large.

"It just happened," she told the newspaper. "I just wanted to give them a better life."