CUMBERLAND, Md. (AP) — An investigation into the stabbing of a nurse at a state psychiatric hospital is focusing on how a patient obtained a 7-inch galvanized metal spike that he allegedly used in the attack, the facility’s chief executive said Tuesday.

Judy Hott, CEO of the Thomas B. Finan Center in Cumberland, said it was not clear Tuesday afternoon where the spike came from or how patient Craig Zello obtained it. She said it was possible the spike was pulled from a gutter on the outside of the building.

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The male nurse, who police say was stabbed in the head, was treated at an emergency room and released after the attack Monday morning, Hott said. No one else was injured.

Zello, 50, of Hagerstown, has been charged with attempted murder, first-degree assault and other offenses. He is being held without bond. Online court records did not indicate that he has an attorney, and he has been represented by public defenders in previous court proceedings.

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Zello was found not criminally responsible on an attempted carjacking charge in 2006, court records show. He was transferred to the Finan Center in August 2012, according to the records.

The Finan Center is an 88-bed facility with about 200 employees that houses mentally ill patients. Some check in voluntarily, and others are committed involuntarily or referred by courts. Patients are barred from possessing weapons.

State police and the facility’s in-house police force are investigating the incident. Hott said staffers are discussing ways to improve safety and security, but no major changes have been made.

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