Jessica Barrymore; Drew Barrymore (inset)
Jessica Barrymore/Facebook; Inset: Sara De Boer/Startraks
's half sister, Jessica Barrymore, was found dead in a car early Tuesday in National City, California, just north of San Diego.
Jessica's body was discovered when a woman trying to leave for work found her driveway blocked by a car, KGTV ABC10 San Diego
She reportedly found Jessica unresponsive and reclined in the seat, an energy drink between her legs, dozens of white pills scattered on the passenger seat. An autopsy had yet to be scheduled.
"Although I only met her briefly, I wish her and her loved ones as much peace as possible, and I'm so incredibly sorry for their loss," Drew said in a statement released to PEOPLE Wednesday.
Though police have not released an identity, Lt. Robert Rounds confirmed to PEOPLE that a female body was found behind the wheel of a car in National City on Tuesday morning.
"She wasn't moving and was unresponsive, and the officers confirmed she was deceased," he said, adding that the cause of death remains unknown as the medical examiner's office continues to investigate.
Drew and her half sister – who would have turned 48 on July 31 and attended the San Diego School of Creative and Performing Arts – had the same father, John Drew Barrymore.
In a cryptic final post on her Facebook
page, Jessica shared a photo from Mystera Magazine
"Life doesn't always introduce you to the people you WANT to meet. Sometimes, life puts you in touch with the people you NEED to meet to Help You, to Hurt You, to Guide You, to Leave You, to Love You, and to gradually Strengthen You into the Person You Were Meant to Become."
"Yes!" Jessica wrote above the message.
Reporting by LIZ MCNEIL