When Corey Haim recently called Jensen LeFlore, his director on the movie Decisions, his mood was markedly different from the upbeat, Frisbee-playing actor on the set of a just a few weeks earlier.

Haim explained that he had just spoken to his 61-year-old mother Judy, who was battling breast cancer. She was not doing well.

"That was the only time I really heard him down," the director tells PEOPLE. "His mom was all Corey had ... He was focused on taking care of his mom. They were living together. He wanted to take care of her."

In the end, it was his mother who called 911 on Wednesday from her Los Angeles area apartment to report Corey had collapsed and wasn't responsive. The actor was later declared dead at the hospital, possibly a victim of an overdose, according to the LAPD.


Living with His Mother
The 38-year-old Haim was staying in Judy's hillside apartment complex in between a spate of acting jobs, as his career – long derailed by drug addiction and erratic behavior – was showing signs of rebounding. But even when he was working, he was always close to his mother, who is divorced from his father; he would call her frequently, and she'd visit him on the set.

"They spent a lot of time together," says actress Angela Cullins, who costarred with Haim in the thriller American Sunset, shot last spring in Canada. "She was battling breast cancer. It was very stressful for him ... It was exhausting, but he took care of her when she needed him."

Haim's agent Mark Heaslip says the actor "has been there for her all the way" as his mother underwent chemotherapy and radiation and lost her hair. "Corey had been attending every doctor’s appointment with his mom. It was amazing how well he supported her," says Heaslip.

During his stay with his mother, Haim came down with flu-like symptoms, including a 101-degree fever. A doctor checked him Tuesday and ordered bed rest.

"He stayed in bed all day through the evening," says Heaslip. "And then in the middle of the night he woke up his mom and said, ‘Mom, can you please come and lie next to me, I’m not feeling very good.’ "


Mother Called 911
Judy got into the bed with her son, then woke up to find him with labored breathing. She told him to lie on his side, and they both fell asleep again. At midnight, she heard her son walking around.

"And then he just collapsed. He just fell over," says Heaslip. "She called for an ambulance."

Now, with her own health uncertain, Judy Haim has lost the closest person in her life. "She is taking this very, very hard," the agent says. "This is all shocking."