A 65-year-old woman was fatally stabbed Monday evening in an apparently unprovoked attack at a Barnes & Noble store, authorities said.

According to ABC News, the victim, identified as Rita Loncharich, was found unresponsive with a knife in her back shortly before 8 p.m., police said. She was transported to a local hospital, where she was pronounced dead.

Police later arrested 40-year-old Antonio Moore, who allegedly admitted to stabbing Loncharich without provocation.

Moore told authorities he experienced “an internal buildup that led to his fight-or-flight response” and said Loncharich was the closest person in the store, according to the probable cause affidavit.

Moore, who had arrived in Palm Beach Gardens about a week earlier from Georgia, was booked on a first-degree premeditated murder charge and is being held without bond. He is scheduled to return to court next month.

Barnes & Noble declined to comment on the ongoing investigation.