TAMPA — The neighborhood is a fortress, encircled by 8-foot walls, named after a medieval Spanish city designed to keep out invaders: Avila.Many drive past its gates, guarded every hour of every day.Few ever see inside.For that reason, it is a magnet for those who will pay for privacy: star athletes, socialites, moneyed professionals.Their 395 homes sit on 900 acres of lush green and lakes.Their golf course, designed by Jack Nicklaus, draws celebrities for an annual tournament hosted by Derek Jeter.The New York Yankees shortstop lived there, before he sold his house to a tennis pro. Teammates Mariano Rivera and Jorge Posada were neighbors.It's a place where homes have six-car garages, theaters and elevators. Where driveways are so long, children trick-or-treat in golf carts. Where if the doorbell rings, the best guess is it's dinner, being delivered from the country club.But on Tuesday night at supper time, residents were opening their doors to investigators. Because the previous night, a neighborhood couple, Dr. Hector and Debra Rivera, had been killed.Some heard the gunshots Monday night. Those who didn't found out fast.Deputies descended. Helicopters hovered. The homeowner's association emailed residents warnings to keep their doors locked.Angie Castellano, 86, stayed inside."I'm scared to death," she said. "We're supposed to have exclusive security."Tony Muniz, the chairman of the Tampa Sports Authority who also chairs Avila's security committee, said most of his neighbors thought the killings were isolated."I think when your friends are murdered, you get the feeling suddenly that you're not secure," Muniz said. "But in the last year, we've had the sheriff's neighborhood liaison review all our security in the neighborhood. All the walls. All the guard stations. We've made improvements in just the last 12 months."There are only two entrances to the neighborhood, the gate at Lake Magdalene Boulevard and the one on N Florida Avenue.Every resident's vehicle has a barcode sticker. Every visitor registers at the guard house. That goes for maintenance crews, newspaper carriers and delivery trucks, too.Video cameras capture the images of each driver and each vehicle and tag. No one can enter without the authorization from a resident.The guards are friendly, but strict. They use radar guns to set up speed traps in the neighborhood. They regulate street parking. The subdivision is constantly patrolled by a slow-moving pickup, guards inside waving to each resident they pass.Muniz said Avila's security personnel had helped detectives review security footage until 5 a.m. He knew the Riveras. Many in Avila did.Among those mourning is resident John Lund, a lawyer, who said he would remain anxious until the case was over.Lund was one of Avila's first residents. He bought in the neighborhood for its safety. His house, like many others, is wired with alarms monitored by both a private security company and the neighborhood guards.Since 1984, he has seen only a handful of burglaries, which prompted security upgrades. Never something like this.But Lund feels no differently about Avila."I don't think anyone believes someone stole their way into the neighborhood," Lund said. "I always felt it's probably the safest neighborhood in the state of Florida."He still does.Times staff writers Mark Puente Danny Valentine contributed to this report. Alexandra Zayas can be reached at [email protected].