The longtime girlfriend of Philip Seymour Hoffman is said to be absolutely devastated by his sudden and tragic death, a source told ShowBiz Spy.

"Mimi is inconsolable. He had his problems, but she thought he was on the road to recovery following his rehab stint. Mimi already had a tough few days, after the recent hoax that claimed Philip had died. She will have to stay strong for the sake of the kids."

Click Here to see photos of Hoffman's children from May 2013.

A friend of Hoffman, screenwriter David Bar Katz, and an unnamed female friend found the Oscar-winning actor in dead and in his underwear in his apartment early Sunday after he never showed up to pick up he and O'Donnel'l's three children. They immediately called police. A needle was also in his arm.

A police officer said, "He was shooting up in the bathroom."

After authorities scanned the apartment they found a total of eight empty glassine envelopes. Five were thrown in a garbage can while the other two were under the bed and one placed on the table.

A female neighbor of O'Donnell said that he was a "troubled soul" and did not seem okay in his last days.

"He did not look well recently-- like he was out of it. I think him and his woman friend were off and on. He lived down here for a long time and was well liked, but everyone kew he had substance-abuse problems."

Hoffman's relative also said, "We're just really devastated that this could happen."

Hoffman was 46-years-old.

Tags: Philip Seymour Hoffman Dead