Sources who claim they were inside the home shortly after a San Jose husband and wife were found shot to death this weekend, say they saw writing on the floor in big black magic marker letters that read: "Sorry, my first kill was clumsy."

Then, on the wall, a much longer, rambling diatribe, in the same permanent lettering. The end allegedly read something like: "I can’t be like you, telling a lie. I can’t love someone without telling them," the sources claimed. Somewhere in the rant was a part about how the wife begged for her life as she was being killed, sources told NBC Bay Area on Tuesday.

The sources asked to remain anonymous to avoid offending the families of victims Golam and Shamima Rabbi, ages 59 and 57, who were killed Sunday in their quiet home on a cul-de-sac on the 3000 block of Lucas Court. It's San Jose's first double homicide of the year, and the first in recent memory to rock the close-knit Bangladeshi community.

Who wrote the messages — and why — has not been revealed. However, police said they don't believe the Rabbis death was a "random act of violence," noting that the suspect was "someone familiar to the family."

The victims were parents of two boys, a 17-year-old student at Evergreen High School; and Hasib, who attends college and is in his early 20s. San Jose police on Tuesday evening said they are looking for Haseeb. He is not yet "considered a suspect," but investigators would like to ask him some questions, they said.

Relatives Mourn Husband, Wife Killed in San Jose

Police, however, would not confirm the messages even existed. Spokesman Albert Morales said no one has been arrested in connection with the killings.

According to a neighbor, the couple’s two sons were in Oakland over the weekend, but no one had seen or heard from the parents since Friday. A relative entered the home at some point on Sunday to check on the couple and found both bodies, along with the ominous messages, sources said. Police were called at 1:47 p.m.

"I can’t ever remember this happening in the Bangladeshi community," said Evergreen Islamic Center Board Member Hasan Rahim, who had known the couple for 30 years. "It’s never happened."

Rahim said he still can’t believe his longtime friends are gone. And he can’t figure out who would want to end their lives.

"I can’t fathom it," Rahim said. "They were so eager to make the community better. They were so soft spoken. I never saw my friend angry or agitated."

If the bodies are released by the Santa Clara County Coroner’s Office on Thursday, Rahim said, as is Muslim tradition, they will be buried the next day at an Islamic cemetery in Livermore.

San Jose police began investigating the deaths of a man and woman in the city’s Evergreen neighborhood. Damian Trujillo reports.

Rahim last saw Golam Rabbi on Friday, two days before his death, at the small mosque for the jumu’ah prayer. He described Golam Rabbi, an engineer, as the type of person who took initiative, but would not take any credit for his leadership.

When the community had to cut down a eucalyptus tree to make way for a newer mosque behind the one on Ruby Avenue, Golam Rabbi offered to take the huge pile of bark and distribute the mulch for neighbor’s gardens.

"He took it upon himself," Rahim said. "And in a few days, the tree was gone."

Shamima Rabbi, an accountant, was also "so gentle, so simple," according to Rahim.

They were "very polite, very humble," Rahim said. "It is difficult to reconcile what happened to people who have such humility, given how peaceful they were."

Rahim said he knew his longtime friend was a hunter, and once said to him, "You must have guns in the home. If you hunt, you must have guns, please be careful," he recalled.

He said Golam Rabbi answered back, "Of course, I'm careful."

San Jose police said the couple were shot "at least once," but would not say what type of weapon was used. In a statement on Monday, police also said "the motive had not been determined."

The deaths have shocked the normally quiet neighborhood. Three bunches of flowers and a candle on Monday marked the garage where the couple lived for about 15 years with their sons.

Neighbor Alan Truong called them "a normal family."

Perhaps their best friend on the street, Fadel Shukry, was among the most taken aback. As his wife cried in the driveway, Shukry described how kind his neighbors were. Golam Rabbi often took care of the Shukry pets, and Shukry would often feed the Rabbi’s fish.

"They were nice people," he said. "So generous. They were the best neighbors I ever had."

NBC Bay Area's Marianne Favro contributed to this report.