NEW YORK (CBSNewYork) — A University of Florida law school graduate has pleaded not guilty to first-degree murder charges in the strangulation death of his ex-girlfriend.

Jason Bohn, 33, was ordered held without bail after entering his plea on Monday.

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The beaten and bruised body of 27-year-old Danielle Thomas was found in the couple’s Astoria apartment on June 26.

According to a criminal complaint, police discovered Thomas’ bruised body laying face up in the bathtub surrounded with bags of ice.

A note found at the scene apparently read, “It was an accident. I had been drinking and I was drunk when I got home. She was already asleep. I woke up and there was fighting between us. When I woke up again she was unconscious.  I am sorry.”

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Bohn told police he had gotten angry and threw Thomas against a wall, prosecutors said.

Bohn’s attorney, Todd Greenberg, said his client has a history of mental issues.

“This may not be a case of ‘whodunnit’ as much as why it happened,” Greenberg told CBS 2. “At that extent I do think that Mr. Bohn’s mental capacity will become an issue in this case.”

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Bohn is being held in protective custody at Bellevue Hospital and will remain there until his next court appearance in September.