PENSACOLA, Florida (CNN) -- Seven people are in custody in connection with the shooting deaths of a Gulf Coast couple known for adopting special-needs children, and one more person is sought, the sheriff of Escambia County, Florida, said Tuesday.
Byrd and Melanie Billings did not have any children together, but they cared for 16 children over the years.
All seven people will face murder charges in the deaths of Byrd and Melanie Billings last week, authorities said. The suspects include a 16-year-old.
"We've got the primary individuals and suspects in custody today," Sheriff David Morgan said. The eighth person is believed to have aided and abetted the crime, he said, and authorities know that person's name and location.
But police would not divulge many details regarding the investigation into the deaths, saying only that the couple was killed during a home invasion robbery. Watch sheriff describe crimes »
Some information uncovered during the investigation, involving elements outside Florida, was turned over to federal authorities in a meeting Monday, the sheriff said.
He identified the seven suspects as:
• Leonard Patrick Gonzalez Jr., 35
• Leonard Patrick Gonzalez Sr., 56
• Wayne Thomas Coldiron, 41
• Gary Lamont Sumner, 30
• Fredrick Lee Thornton, 19
• Donald Ray Stallworth, 28
• An unidentified juvenile, 16
Prosecutors plan to charge the teen suspect as an adult, Escambia County State Attorney Bill Eddins said.
The younger Gonzalez, a former National Guard member, is believed to have been the organizer of the crime, Morgan said.
He has said the crime was "very well-planned and methodical." Watch surveillance video of the home invasion »
Gonzalez isn't the only suspect with military experience. Stallworth is a staff sergeant and maintenance mechanic with the 1st Special Operations Aircraft Maintenance Squadron, based at Hurlburt Field in Fort Walton Beach, Florida, according to Lt. Mark Lazane of Air Force Special Operations. He was arrested Tuesday in Alabama.
Sumner, Thornton, Stallworth and the juvenile are from Okaloosa County, Florida -- one county away from Escambia County, where the crime occurred -- and knew each other from an auto detailing group, Morgan said.
Authorities initially said the senior Gonzalez faced charges of evidence tampering for allegedly trying to disguise a vehicle spotted at the Billingses' home. However, charges against him were upgraded to murder, the sheriff's office said Tuesday.
Police have released two surveillance tapes taken from the front and rear of the Billingses' home. Each shows a vehicle pulling up to the property and five people dressed in black and wearing masks entering the home through two entrances, including a utility door left unlocked, something Morgan said is not uncommon in the community. Authorities believe that drivers remained in both of the cars.
Both the Billingses were shot multiple times, Morgan said.
Items were taken from the home "that you would normally expect to be taken in a robbery," Escambia County State Attorney Bill Eddins said. The items included a safe, but neither Eddins nor Morgan would divulge additional items or say whether any stolen items had been recovered.
Investigators know who the actual gunmen were, Morgan said, but he would not tell reporters. Watch experts describe the "military-style" attack »
Asked whether the suspects had expressed remorse, the sheriff said, "Everyone expresses remorse when they're caught."
Eddins said prosecutors have not decided whether the seven will be tried together or whether to seek the death penalty. Four of the suspects were to appear in court Tuesday, he said.
Melanie Billings' biological daughter, Ashley Markham, said the couple initially had 17 children. Byrd and Melanie Billings each had two biological children; the rest were adopted. Three have died over the years, she said. The couple had no biological children together . Watch Markham say, "Love was never scarce" »
Morgan, however, has said the couple had 16 children, with two who have died and others who have grown older and no longer live in the Billingses' home.
Nine of the couple's children was home at the time of the incident, Morgan said, and police believe that three of them saw the intruders. One managed to flee the home and seek help at a neighbor's house, the sheriff said.
The Billingses lived in Beulah, west of Pensacola, near the Alabama state line.
CNN's Carolina Sanchez, Colleen Wright, Adam Levine and David Mattingly contributed to this report.