The "soft-spoken" 42-year-old Indian software engineer killed five of his family members before shooting himself using two recently purchased pistols, police said on Wednesday, indicating that the crime was likely related to "family dynamics and personal relationships."

The lone survivor of the "unimaginable violence", the wife of the engineer who escaped with multiple gunshot wounds, was in a critical condition at a local hospital, police said and ruled out financial woes as the motive behind the slaying.

While police have not revealed her name, relatives identified her as Abha.

Investigators are not certain what triggered the violence, but they believe that it was some kind of family feud which made Devarajan go on a shooting rampage.

Besides his son and daughter, Devan Kalathat, whose original name is Devarajan, also shot his brother-in-law Ashokan, a software professional, his wife Suchitra (30) and daughter Akhila (10).

Investigators said Devarajan used two legally purchased .45 caliber semiautomatic pistols. One of the guns was purchased six weeks ago, and the other was purchased less than two weeks ago at about the time his relatives came to visit the family from India.

"On the surface there wasn't a financial reason that would explain this. There were apparent personality problems and the motive was likely related to family dynamics and personal relationships," Santa Clara police chief Lt Phil Cooke was quoted as saying by the local media.