Philip Seymour Hoffman’s Drug Hell: He Was Spending $10K Per Month On Heroin, Oxycontin - Purchased Lethal 'Brick' Before Death

The death of Philip Seymour Hoffman came as a shock to his fans, but was anything but surprising to those close to him.

Found with a hypodermic needle still in his arm on Sunday morning, an insider reveals exclusively to RadarOnline.com just how bad Hoffman's drug habit had escalated -- spending upwards of $10,000 per month on heroin and using the prescription drug, Oxycontin.

"He was what we call a heavy 'red liner,'" the source told RadarOnline.com.

"That means he liked to shoot heroin with a needle, but he also sniffed it daily. And he was majorly hooked on Oxy, too."

Hollywood & Heroin: 28 Stars Who Used What Killed Cory Monteith

In fact, Hoffman, 46, had fallen so far off the wagon of sobriety that the source tells RadarOnline.com he was buying bundles and bricks at a time.

"He just bought five bundles of dope last week," the source claimed.

A bundle is 10 bags of heroin, and there are five bundles in a brick.

Hoffman had struggled with substance abuse in his early career and first went to rehab after graduating from New York University in 1989.

"Heroin is one of the cheaper drugs, but Hoff wasn't buying the cheap stuff," the source said.

"Still, to be spending 10 grand, he was using hard."

As RadarOnline.com reported on Sunday, a personal assistant reportedly found Hoffman in his Manhattan apartment and called 911.

"On Sunday, February 2, 2014, at approximately 1136 hours police responded to a 911 call for an aided male... upon arrival, officers located a 46-year-old male, unconscious and unresponsive, lying on the bathroom floor," the NYPD said in a statement.