"I told him I have to go home," said Gallo, who was going to start a new job laying tile the next day, but the pair went to the bikini bar anyway.
"I told him we've got to stop" drinking, but before Gallo knew it someone had ordered them a round of shots, he said.
Gallo told the detectives he avoided shots of hard liquor, because he wasn't able to handle it. "The last time I did that at a family party things got out of hand and I blanked out," he said.
Gallo told investigators he couldn't remember how he and Rivera ended up in Fullerton and he was unfamiliar with the area.
"I don't remember getting in the car or leaving the place," he said. "The only thing that woke me up was the hit."
Later, he said, "I guess while I'm driving home I blanked out ... We were trying to get home and we got lost. I don't know anyone in Fullerton."
Gallo said he was surprised he was in the driver's seat because his license was suspended for not completing the terms of his conviction for driving under the influence in 2006.
"I don't know why I was driving. I'm not allowed to drive," he told the investigators.
Earlier Thursday, jurors watched a police interview with witness Esteban Quiroz, who was trying to make a left turn at the same intersection just seconds before the wreck.
Quiroz, 34, told police in the April 9, 2009 videotaped interview that he got a turn signal and was inching into the intersection when he saw a red minivan traveling about 70 or 80 mph approaching from his left.
Seconds later, as Quiroz watched, the minivan ran the red light and T-boned the car carrying the victims, he told officers.
"It was just flying. You don't expect a car to be going that fast toward a red light. Next thing I knew, it was on top of the gray car," he said. "What was really apparent ... is that the van was not going to stop."
Quiroz's car was swiped by the victims' car as it spun around after the impact and his airbag deployed, knocking his glasses off his face. He was not seriously injured.
Gallo has pleaded not guilty to the murder charges, as well as to felony hit-and-run and driving while intoxicated and causing injuries to two other people.
Gallo, whose blood-alcohol level was nearly three times the legal limit, according to police, could face a maximum sentence of more than 50 years to life in prison if convicted.
The remainder of Gallo's videotaped interview will be played for jurors when court resumes on Monday.