PENSACOLA (AP) – Byrd and Melanie Billings had a growing brood of adopted children with autism, Down syndrome and other disabilities, and took care to make their nine-bedroom house a safe place for them, wiring it with surveillance cameras in every room.

It was those cameras that captured images of the masked men who shot the wealthy couple to death in a break-in executed with chilling precision.

Authorities made three arrests over the weekend, plus another arrest announced Monday evening, but the mystery around town only deepened, when Sheriff David Morgan said that as many as eight people in all may have been involved and that the crime appeared to have “numerous motives,” though robbery was the only one he would mention.

“Mr. Billings was well-to-do. He was an entrepreneur and he opened his home to the community. You are asking me to speculate on a motive. That could have been one reason,” Morgan said, likening the killings to the 1959 slayings of a Kansas farm family that were chronicled by Truman Capote in the book “In Cold Blood.”

The video from last Thursday showed three armed, masked men arriving in a red van, entering through the front of the house and then returning to the vehicle. Others dressed in what the sheriff called “ninja garb” went in through an unlocked utility door in the back. They were in and out in under 10 minutes.

The sheriff would not say what, if anything, was stolen.

Some of the nine children in the house at the time were sleeping, but several others saw the break-in, authorities said. One left the house and went to get a neighbor, who called 911.

“I think you’ll find this particularly chilling and here’s why: We have a team that enters at the rear of the home and another that enters at the front of the home,” Morgan said. “It leads me to believe this was a very well-planned and methodical operation.”