The next night, August 9, 1969, six Family members—Leslie Van Houten, Steve "Clem" Grogan, and the four from the previous night—rode out at Manson’s instruction. Displeased by the panic of the victims at Cielo Drive, Manson accompanied the six, "to show [them] how to do it." After a few hours’ ride, in which he considered a number of murders and even attempted one of them, Manson gave Kasabian directions that brought the group to 3301 Waverly Drive. This was the home of supermarket executive Leno LaBianca and his wife, Rosemary, a dress shop co-owner. Located in the Los Feliz section of Los Angeles, it was next door to a house at which Manson and Family members had attended a party the previous year.
According to Atkins and Kasabian, Manson disappeared up the driveway and returned to say he had tied up the house's occupants; then he sent Watson up with Krenwinkel and Van Houten. In his autobiography, on the other hand, Watson stated that, having gone up alone, Manson returned to take him up to the house with him. After Manson pointed out a sleeping man through a window, the two of them entered through the unlocked back door. Watson added that, at trial, he "went along with" the women's account, which he figured made him "look that much less responsible."
As Watson tells it, Manson roused the sleeping Leno LaBianca from the couch at gunpoint and had Watson bind his hands with a leather thong. After Rosemary LaBianca was brought briefly into the living room from the bedroom, Watson followed Manson’s instructions to cover the couple’s heads with pillowcases. He bound these in place with lamp cords. Manson left, sending Krenwinkel and Leslie Van Houten into the house with instructions that the couple be killed.
Before leaving Spahn Ranch, Watson had complained to Manson of the inadequacy of the previous night's weapons. Now, sending the women from the kitchen to the bedroom, to which Rosemary LaBianca had been returned, he went to the living room and began stabbing Leno LaBianca with a chrome-plated bayonet. The first thrust went into the man's throat.
Sounds of a scuffle in the bedroom drew Watson there to discover Mrs. LaBianca keeping the women at bay by swinging the lamp tied to her neck. After subduing her with several stabs of the bayonet, he returned to the living room and resumed attacking Leno, whom he stabbed the balance of twelve times with the bayonet. When he had finished, Watson carved "WAR" on the man's exposed abdomen. He stated this in his autobiography. In an unclear portion of her eventual grand jury testimony, Atkins, who did not enter the LaBianca house, possibly said she believed Krenwinkel had carved the word. In a ghost-written newspaper account based on a statement she had made earlier to her attorney, she said Watson carved it.
Returning to the bedroom, Watson found Krenwinkel stabbing Rosemary LaBianca with a knife from the LaBianca kitchen. Heeding Manson’s instruction to make sure each of the women played a part, Watson told Van Houten to stab Mrs. LaBianca too. She did, stabbing her approximately 16 times in the back and the exposed buttocks. At trial, Van Houten would claim, uncertainly, that Rosemary LaBianca was dead when she stabbed her. Evidence showed that many of Mrs. LaBianca's forty-one stab wounds had, in fact, been inflicted post-mortem.
While Watson cleaned off the bayonet and showered, Krenwinkel wrote "Rise" and "Death to pigs" on the walls and "Healter [sic] Skelter" on the refrigerator door, all in LaBianca blood. She gave Leno LaBianca fourteen puncture wounds with an ivory-handled, two-tined carving fork, which she left jutting out of his stomach. She also planted a steak knife in his throat.
Hoping for a double crime, Manson had gone on to direct Kasabian to drive to the Venice home of an actor acquaintance of hers, another "piggy." Depositing the second trio of Family members at the man's apartment building, he drove back to Spahn Ranch, leaving them and the LaBianca killers to hitchhike home. Kasabian thwarted this murder by deliberately knocking on the wrong apartment door and waking a stranger. As the group abandoned the murder plan and left, Susan Atkins defecated in the stairwell.