TAMPA, Fla. - The family employee under arrest in the shooting deaths of a retired doctor and his wife at their home in an exclusive gated community in Tampa, Fla., had a rocky relationship with the couple and was suspected by them of stealing jewelry from their home, authorities say.

Julian Ospina Florez, 31, of Tampa, was arrested Tuesday night after police found the apparent murder weapon in the home of his boss, Debra Rivera, 55, who was found shot dead Monday night along with her husband, retired doctor Hector Rivera, 76.

Florez, 31, was a driver and personal assistant for Debra Rivera, who worked from home selling jewelry and accessories.

"The relationship between Miss Rivera and him was she had become distrustful of him. She had reported a theft a week or so before at her residence of some jewelry that had been stolen,"  Hillsborough County Sheriff David Gee said at a late-night press conference on Tuesday.

"He was not in good standing with her," the sheriff added.

Florez, a naturalized citizen who came to the U.S. from Colombia in 1999, made his first appearance in a Tampa courtroom today to face two counts of first-degree murder.  He was ordered held in the Hillsborough County Jail without bond until Friday, when a hearing will likely be held.

Florez is said by authorities to not be cooperating in the case.

Hillsborough County authorities said Florez drove Debra Rivera to a trade show at the Ritz-Carlton Hotel in Sarasota Monday to buy jewelry and other merchandise for her business, Distinctive Creations.

Around 8 p.m. that night, authorities began receiving calls from neighbors in the couple's exclusive neighborhood of multi-million dollar mansions to report gunshots.  They also received a call from Florez, who called 911 from inside the home to report a shooting and attack by an intruder.

When authorities arrived, they found Debra Rivera dead in one of the 11,000-square-foot mansion's six bathrooms, and her husband lying dead on the front lawn, reportedly gunned down while returning home from watching a football game.

Inside the home, they found Florez, unharmed, and no sign of forced entry.

They also found the 9 mm gun used to shoot the couple,  Gee said. Investigators later found a box of ammunition in Florez's car, and a receipt showing he had bought the ammunition from a  Walmart on Dec. 7.

"It was a very brutal killing," the sheriff said.  "There was no question that his intent was to make sure that nobody survived this attack."

The exclusive Avila neighborhood in which the couple lived is protected by 8-foot high walls and surveillance cameras, requires residents to have a bar code on their cars, and for visitors to go through security checks.

Former and current residents of the neighborhood reportedly include former major league baseball player and manager Lou Piniella, New York Yankees catcher Jorge Posada and former Tampa Bay Buccaneers coach Tony Dungy.

The couple had a son together and Hector Rivera had three children from a previous marriage, according to a family member.

ABC News' Michael S. James, Robin Reese and Dean Schabner contributed to this report.