The conviction of Earnest Lynn Ross on federal firearms charges last week is the first step in protecting the public from a lifelong violent criminal, say local law-enforcement officers who have dealt with him since he was 16.

Mr. Ross, 43, was convicted Friday in Sherman on two federal charges of unlawfully carrying a weapon. A sentencing date has not been set, but officers say he is likely to receive 20 years in federal prison.

"His criminal career has hopefully come to an end," said Denton County Sheriff Benny Parkey, whose investigators played a key role in Mr. Ross' June arrest in a part of Dallas that lies in Denton County.

Authorities say Mr. Ross led a gang that carried out at least 70 home-invasion robberies and about 10 burglaries in North Texas since 2005.

Their exploits, performed with SWAT-like precision, paid handsomely – at least $1 million, authorities estimate. Officials say the gang plowed some of the money back into other ventures, some of them criminal, including mortgage fraud.

For the past two years, law-enforcement officers in Denton, Dallas, Rockwall, Ellis, Collin and Tarrant counties had been investigating home-invasion robberies that they now believe were committed by Mr. Ross and several other men working together.

Dallas police arrested a man who they believed was involved and learned from him that Mr. Ross had threatened to kill Sheriff Parkey and bragged that he had him in his gun sights twice. They notified the sheriff, who offered his special-operations team to help.

Denton County detectives worked with Dallas officers and devised a Dallas sting that led to the arrests of Mr. Ross and three other men.

"This is the beginning," said sheriff's Lt. David Scott, who supervised the sting and also arrested Mr. Ross in 1981 in connection with the sexual assault of a 14-year-old Denton girl. "He still has numerous other state charges. It's my understanding he'll have to serve all the state sentences before he begins serving the federal sentence.

"Between all of that, he'll be off the streets for a significant amount of time."

Mr. Ross previously was arrested in the 1993 murder of a 19-year-old gang member. He was convicted three years later and got a life sentence.

But an appeals court tossed out the murder conviction. In 2001, as he was about to be retried, Mr. Ross pleaded guilty to a reduced charge of aggravated assault. He was released the same year.