A special jury in California ruled on Thursday that two women killed themselves and their six adopted children in a murder-suicide in March 2018, officially determining the cause of the family’s fatal plunge over a 100-foot cliff.

The authorities had long believed that Sarah Hart and her wife, Jennifer Hart, had purposely driven their sport utility vehicle over a Northern California cliff with their six children in the car, days after learning they were under investigation by child welfare officials. The special coroner’s jury — which was empaneled to determine manner of death and not criminality — reached a unanimous decision in about an hour of deliberation after hearing chilling details over two days of testimony.

Investigators found Sarah Hart had recently performed internet searches about suicide, Benadryl dosages and whether drowning was painful, according to The Associated Press. Sarah Hart had 42 doses of generic Benadryl in her system, an investigator testified, while Jennifer Hart, the driver, had a blood alcohol concentration of 0.102 percent when she drove the car off the cliff. In California, it is illegal for drivers to have a level of 0.08 percent or higher.

An investigator said the driver deliberately stepped on the gas.

“They both decided that this was going to be the end,” said Jake Slates, a California Highway Patrol investigator, according to The Associated Press. “That if they can’t have their kids that nobody was going to have those kids.”