A 41-year-old San Francisco plumber who was on a losing streak at local casinos and faced eviction for not paying his rent was found guilty Monday of slaughtering a family of five inside their Ingleside neighborhood home after targeting them for robbery.

On its seventh day of deliberations, the San Francisco Superior Court jury found Binh Thai Luc, an undocumented Vietnamese immigrant with a violent criminal past, guilty of five counts of murder in the massacre of the Lei family on March 23, 2012.

The victims’ bludgeoned bodies were found covered in blood and household cleaning products in various rooms of the row house on Howth Street, which had been flooded with water. The damage was so severe and the scene so chaotic that investigators didn’t initially know if they were dealing with a quintuple murder or a murder-suicide.

Prosecutors said Luc used a hammer to commit one of the worst mass homicides in modern San Francisco history, though the weapon was never found. The defendant was also found guilty of five counts of attempted robbery and two counts of burglary.

Because Luc was convicted of murder with special circumstances — in this case, lying in wait and committing multiple killings — he faces life in prison without the possibility of parole. The charges made him eligible for the death penalty, but the district attorney’s office did not pursue that punishment. Judge Carol Yaggy will set a sentencing date Tuesday.

“This was a very gruesome, brutal murder, and we’re pleased we’re getting some accountability for the family and for the community,” District Attorney George Gascón said.

Luc said nothing after the verdict was read. Wearing a light-blue collared shirt and black vest, he leaned in occasionally to whisper to his defense attorney, Mark Goldrosen.

“He was quite disappointed,” Goldrosen said outside the courtroom. “He understands that this is the beginning of the process and there are appellate procedures.”

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None of Luc’s family members, who occasionally attended the trial, came Monday, nor did relatives of the victims.

Police arrested Luc shortly after the killings at a hotel in San Mateo, where investigators found him reading an article in The Chronicle about the crime on his computer, prosecutors said.

He was found guilty of killing Hua Shun Lei, 65; his wife, Wan Yi Wu, 62; their daughter, Ying Xue Lei, 37; their son, Vincent Lei, 32; and his wife, Chia Huei Chu, 30.

Vincent Lei’s 12-year-old niece discovered the carnage at 7:45 a.m. and ran out of the home screaming, “Mommy, bodies! Bodies!” A witness later heard the girl’s mother, Nicole Lei, on the phone, yelling hysterically, “They took the money! The money is gone!” prosecutors said.

While authorities didn’t have an eyewitness place Luc at the scene of the crime, Assistant District Attorney Eric Fleming used numerous pieces of physical evidence to link Luc to the killings.

Investigators said Vincent Lei’s blood was spattered on Luc’s jeans, which were discovered at his home. Inside the Lei home, crime scene technicians reported finding Luc’s blood on a pack of cigarettes, a receipt and a cabinet drawer. Luc had a cut on his hand when he was arrested shortly after the crime.

Police also found a fingerprint on a bottle of window cleaner inside the home that matched Luc’s right index finger, prosecutors said. The bodies were covered with bleach and other products, and the killer flooded the home by turning on faucets and detaching pipes under sinks.

Goldrosen didn’t dispute that Luc was at the scene around the time of the killings. Instead, he argued that someone else attacked the family, suggesting the real killer could have been one of two notorious Chinatown gangsters — or possibly a former boyfriend of one of the victims.

Goldrosen argued that the prosecution didn’t establish a motive for the crimes, which he characterized as “gang-style, loan-shark-style” slayings.

Fleming told the jury that Luc killed the family members while robbing them. He frequented Artichoke Joe’s Casino in San Bruno and had dumped thousands of dollars gambling in the weeks before the crime. The prosecution even said Luc lost money at a casino on the night of the massacre.

The jury was told Luc had been served an eviction notice for not paying his rent, a debt he settled immediately after the killings. When he was arrested, he had $6,518 in cash. Prosecutors said the Lei family kept thousands of dollars in the home, and that Luc knew Vincent Lei from local mah-jongg games.

Before the killings, Luc was convicted in 1998 of committing an armed robbery at a Chinese restaurant in San Jose. After he served eight years in San Quentin State Prison, officials handed him over to federal immigration authorities for deportation back to his home country of Vietnam.

Vietnamese authorities, however, refused to provide Luc with travel documents, and he was released from custody as required by federal law.

Evan Sernoffsky is a San Francisco Chronicle staff writer. Email: esernoffsky@sfchronicle.com Twitter: @EvanSernoffsky