A disturbing message was found scrawled in black marker on the floor of a San Jose home where a double murder was carried out, according to reports on US news networks.

The message read: "Sorry, my first kill was clumsy."

A report on NBC Bay Area quoted sources who wished to remain anonymous, but who claimed to have been inside the house where Golam Rabbi, 59, and his wife Shamima, 57, were killed.

Another, longer and more rambling message was reportedly written on the wall and was directed at the couple's oldest son, according to local ABC station KGO.

It included the line: "I can't be like you telling a lie. I can't love someone without telling them."

Somewhere in that message it reportedly said that Shamima had begged for her life.

Police have not confirmed that the messages existed.

The Rabbi couple were killed on Sunday on a quiet residential road in the Evergreen neighbourhood of San Jose.

The two had been shot, police said, in a double murder that has shocked the local community.

The bodies were discovered by a family member who entered the home on Sunday to check on the couple, reports said.

The Bangladeshi couple were described as long-term residents of the area who were active in the local community and had been volunteers at the Evergreen Islamic Center and the South Bay Islamic Association.

The couple had two children, Omar, 17, and Hasib, who is in his early 20s.

Police has said they would like to speak to Hasib but have not been able to contact him.

They said he was not yet "considered a suspect", according to the NBC report.