A former top-ranking Mexican police official, fired over his alleged ties to drug-traffickers, was shot to death yesterday outside his lawyer's office in the border city of McAllen, Tex., local police said.

As a top official of Mexico's federal judicial police in the 1980s, Guillermo Gonzalez Calderoni arrested some of the country's most notorious drug lords. But in 1993 he was fired over accusations that he was protecting drug shipments to the United States.

He fled to the United States, where a federal judge denied Mexico's extradition request. Mexican officials sought Calderoni on charges of torture, illegal enrichment and abuse of authority. Mexican media reports said he had been living in McAllen, assisting U.S. officials in drug investigations.

Calderoni was best known for his accusations against former president Carlos Salinas de Gortari. In 1996 he said Salinas and his brother, Raul, were in business with drug traffickers. Then in 2000 he alleged that Salinas had ordered the assassinations of two rival political activists during his 1988 presidential campaign.

Raul Salinas is serving a 27-year prison sentence for planning the murder of his former brother-in-law, Jose Francisco Ruiz Massieu, then secretary general of the ruling Institutional Revolutionary Party. Carlos Salinas, largely disgraced by Raul's activities, has been living in self-imposed exile in Europe since his presidential term ended in 1994.

Will Glaspy, a spokesman for the Drug Enforcement Agency in Washington, said that under DEA policy he could not confirm whether Calderoni had been cooperating with U.S. officials or was under federal protection.

McAllen police said Calderoni, 54, was shot once in the head shortly before 11 a.m. yesterday as he and another man sat in his car after leaving the office of Roberto Yzaguirre, an attorney who represented Calderoni in his extradition case.

"He had just left the building and entered his vehicle," said Officer Alfonso Cantu, a police spokesman. "Somebody apparently approached him on the driver's side and fired one shot into the vehicle."

Calderoni was taken to McAllen Medical Hospital, where he was pronounced dead at 12:24 p.m. The other man, whom Cantu would not identify, was not hurt and was being questioned by police yesterday.

Police had made no arrests in the case late yesterday and said they had no motive or suspects in the killing.

"We're treating this as a regular homicide," Cantu said. "People have been asking if our federal agencies are getting involved or if Mexican authorities are getting involved in this investigation. All I can tell you is at this time we're the only department investigating the case.

Cantu said the Rio Grande Valley had seen several drug- and gang-related killings in recent months, but none in McAllen. He said McAllen, a city of 110,000 people, averages fewer than 10 homicides a year.

"This might be our first for the year," Cantu said.

Sullivan reported from Mexico City.