The brutal murder of 65-year-old immigrant Hua Shun Lei from Taishan of South China's Guangdong province, together with four family members at their San Francisco home, came as a shock to the city's Chinese community.

Saddened mourners laid flowers at the entrance to Lei's home, while teachers and students from the middle school where he taught in China set up memorial pages on their alumni website.

Lei, his wife Wan Yi Wu, 62, daughter Ying Xue Lei, 37, son Vincent Lei, 32, and his son's girlfriend Chia Huei Chu, 30, were found dead on March 23 at their two-story house near the City College of San Francisco.

In a statement, San Francisco Mayor Ed Lee called the killings a "terrible tragedy".

On Wednesday, a Vietnamese man, Binh Thai Luc, 35, was charged by prosecutors with five counts of murder with special circumstances of committing multiple murders, robbery and burglary.

A motive for the murder has not been determined.

To Lei's co-workers at R & G Lounge, a Chinese restaurant in downtown San Francisco where he was employed for the past 18 years after immigrating to the US, Lei was respected for his hardworking, positive attitude and broad knowledge.

Lei's neighbors described his family as quiet and nice. Lei and his wife had two properties on the same street.

The house where they were killed is registered under the name of their daughter, Ying Xue Lei, who was a software engineer at Quantitative Medical Systems in Emeryville, according to Roxanne Albertoli, an administrative assistant with the company. "She was a wonderful person, she didn't deserve this," Albertoli said.

Owner Huang Jian closed the restaurant for one hour on Monday to hold a memorial service for Lei, and more than 60 employees gathered at lunch time to mourn the death of their co-worker.

"I am too sad to talk and can't sleep well at night. We will try our best to help out Lei's family," Huang told China Daily on Wednesday.

Luc made his initial appearance in court on Wednesday. He also received a special circumstance of lying in wait in the death of Vincent Lei.

According to The Associated Press, those enhancements make Luc eligible for the death penalty if convicted, though prosecutors likely will not pursue that sentence, said Omid Talai, a spokesman for the district attorney's office.