Accused murderer Ray Clark was so desperate to hide his heinous handiwork that he allegedly broke the bones and mangled the body of a strangled Yale grad student to fit it through a wall opening the size of a computer screen, The Post has learned.

“He just crushed her in there. She was like mush — she was so smashed up you couldn’t recognize her,” said a source, who gave The Post disturbing new details of Clark’s moves after Annie Le’s gruesome slaying.

Le’s body, the source said, was found in a utility space in a bathroom wall near the basement lab where she had been working the day she vanished.

In his haste to cover his tracks after Le was killed, Clark accidentally tripped a fire alarm — possibly with his own or Le’s employee swipe card, the source said.

Clark had used both his and Le’s cards to access various areas of the lab after her murder — and those swipe cards can be used to sound a fire alert, according to the source.

“He didn’t mean to set off the alarm,” the source said.

Clark was seen on video after the building was evacuated, holding his head in his hands.

Before Le was even reported missing, two rookie cops who talked to Clark after the fire alarm went off suspected he was up to no good, the source noted.

“They knew something was off with the guy — he was nervous,” said the source.

“He was acting weird, he was ghost white. His answers weren’t making any sense. He was stuttering, and trying to stand in front of a chemistry tray with his arms crossed, trying to hide something.”

Investigators have said Clark aroused suspicion when he was seen trying to clean the lab and hide equipment that later turned out to contain blood splatters.

According to the source, Clark was “a control freak” who insisted on lab cleanliness and “had issues” with the way Le kept her lab and her research mice.

“She wasn’t clean, and it made him mad.”

Le was last seen entering her lab building at around 10 a.m. on Sept. 8 and was reported missing that night. Her body was found Sept. 13, the same day she was to wed Columbia grad student Jonathan Widawsky on Long Island.

A “foul odor” led investigators to her body, the source said.

The space where Le was found — 8 inches deep and covered by a metal panel “the size of a computer screen” — houses a vertical and a horizontal water pipe.

Her killer had to maneuver her body around the pipes, according to the source.

“I’ve been doing this a long time, and I’ve never seen anything like that. This guy’s twisted.”