On the night of August 8, 1969, Tex Watson took Susan Atkins, Linda Kasabian, and Patricia Krenwinkel to "that house where Melcher used to live", as Manson had instructed him, to "totally destroy" everyone in it, and to do it "as gruesome as you can". The occupants of the house at 10050 Cielo Drive that evening were movie actress Sharon Tate, who was 8½ months pregnant and the wife of film director Roman Polanski; her friend and former lover Jay Sebring, a noted hairstylist; Polanski's friend and aspiring screenwriter Wojciech Frykowski; and Frykowski's girlfriend Abigail Folger, heiress to the Folgers coffee fortune and daughter of Peter Folger. This specific house was chosen because both Watson and Manson had been there on several occasions, and Watson was familiar with the layout.
The murder team arrived at Cielo Drive just past midnight on August 9, 1969. Watson climbed a telephone pole near the entrance gate and cut the phone line to the house. The murderers backed their car to the bottom of the hill that led to the estate and walked back up to the house. They thought that the gate might be electrified or equipped with an alarm, so they climbed an embankment to the right of the gate and entered the grounds. Headlights approached them from within the angled property, and Watson ordered the women to lie in the bushes. He stepped out and ordered the approaching driver to halt. Steven Parent had been visiting the property's caretaker William Garretson, who lived in the guest house. Watson leveled a .22-caliber revolver at Parent, and the frightened youth begged him not to hurt him, claiming that he would not say anything. Watson lunged at Parent with a knife, giving him a defensive slash wound on the palm of his hand that severed tendons and tore the boy's watch off his wrist, then he shot him four times in the chest and abdomen, killing him. Watson ordered the women to help push the car farther up the driveway. Watson next cut the screen of a window, then told Kasabian to keep watch down by the gate; she walked over to Parent's car and waited. Watson removed the screen, entered through the window, and let Atkins and Krenwinkel in through the front door. He whispered to Atkins and awoke Frykowski who was sleeping on the living room couch. Watson kicked him in the head, and Frykowski asked him who he was and what he was doing there. Watson replied, "I'm the devil, and I'm here to do the devil's business." On Watson's direction, Atkins found the house's three other occupants with Krenwinkel's help and forced them to the living room. Watson began to tie Tate and Sebring together by their necks with rope which he had brought, and he slung it over one of the living room's ceiling beams. Sebring protested the murderers' rough treatment of the pregnant Tate, so Watson shot him. Folger was taken momentarily back to her bedroom for her purse, and she gave the murderers $70. Watson then stabbed Sebring seven times. Frykowski's hands had been bound with a towel, but he freed himself and began struggling with Atkins, who stabbed at his legs with a knife. He fought his way out the front door and onto the porch, but Watson caught up with him, struck him over the head with the gun multiple times, stabbed him repeatedly, and shot him twice. Kasabian had heard "horrifying sounds" and moved toward the house from her position in the driveway. She told Atkins that someone was coming in an attempt to stop the murders. Inside the house, Folger escaped from Krenwinkel and fled out a bedroom door to the pool area. Krenwinkel pursued her and caught her on the front lawn where she stabbed her and tackled her to the ground. Watson then helped finish her off; her assailants stabbed her a total of 28 times. Frykowski struggled across the lawn, but Watson murdered him with a final flurry of stabbing. Frykowski suffered 51 stab wounds, and had also been struck 13 times in the head with the butt of Watson’s gun, which bent the barrel and broke off one side of the gun grip, which was recovered at the scene. In the house, Tate pleaded to be allowed to live long enough to give birth, and offered herself as a hostage in an attempt to save the life of her unborn child, but both Atkins and Watson stabbed Tate 16 times, killing her. Manson had told the women to "leave a sign-something witchy", so Atkins wrote "pig" on the front door in Tate's blood.