PITTSBURG -- A senior editor for PC World Magazine was shot to death in his home in what police described as a drug-related attack, according to authorities, but late Wednesday the victim's son asserted that he grew and stored medical marijuana at the home with his parents' permission.

Rex Farrance, 59, the San Francisco-based magazine's senior technical editor, was shot in the chest after four masked men broke into his home in a suburb east of the city around 9 p.m. Tuesday, Pittsburg police said.

The assailants also pistol-whipped Farrance's wife, Lenore Vantosh-Farrance, 56, a registered nurse. She called 911, but the attackers fled before officers arrived.

"We have substantial reason to believe that the victim and his wife were involved in the possession and, potentially, the distribution of illegal narcotics," said Pittsburg police Inspector John Conaty, who declined to specify what type of drugs were involved.

No arrests were immediately made in Pittsburg's first homicide of the year, Conaty said.

A phone call to Vantosh-Farrance was not immediately returned late Wednesday.

The couple's son, Sterling Farrance, 19, blasted the police assertion that they were involved with illegal drugs, saying he grew and stored medical marijuana at the home with his parents' permission.

"I have a prescription. I'm a patient. It was medical," Sterling Farrance told the San Francisco Chronicle. "This one officer I remember at the house, he had this predisposition to think it was all illegal."

Colleagues at PC World described Farrance as a fitness buff, rock-music fan and a dedicated husband and father who excelled at his job.

"We're all in shock here," said Denny Arar, a PC World senior editor. "Rex loved his work. He really cared about covering technology in a way that was useful for readers. He cared a lot about people, period, including his co-workers."

Jeff Edman, who leads PC World Communications, said Farrance was a senior technical editor and a 19-year employee at PC World.

"We are shocked and deeply saddened by the news of Rex's untimely death, and our thoughts and prayers are with them at this time," Edman said. "We will miss not only his many contributions, but also his friendship."

Neighbor Herculano Darosa, 54, said he was shocked at the police's allegation that the couple were drug users or dealers.

"He looked nice to me," Darosa said of Rex Farrance.