BURRILLVILLE — In the wake of a shooting, the overseers of Zambarano Hospital have canceled their contract with a North Providence security company, asserting that one of the company’s employees brought a gun onto the campus in violation of policy.

The guard, Todd Brown, allegedly fired a single shot at a knife-wielding intruder in a vacant building on the campus Sunday night. The man ran away, and authorities still had not found him as of late yesterday afternoon.

Brown’s employer, Industrial Security and Investigators, had just recently secured its contract with the Rhode Island Department of Mental Health, Retardation & Hospitals, which oversees the hospital.

Security personnel from the company were informed of the campus’ weapons ban before they started their job at the hospital last week, according to a department spokeswoman, Laurie Petrone.

MHRH ended its contract with the security company on Tuesday.

“What is most important is the health and safety of the patients and the staff up at Zambarano Hospital,” Petrone said yesterday. “We view this as a serious matter.”

The decision also affects the security arrangement at Eleanor Slater Hospital’s other campus in Cranston, Petrone said.

The department is not aware of any other security guards from the company carrying weapons on either campus, she added.

The North Providence company’s director of operations did not immediately respond to a request for comment late yesterday.

MHRH has a fallback security plan in place at both facilities.

Its in-house security team is handling the Zambarano campus and both the Capitol Police and the state police will assist with any security issues in Cranston, she said.

Now, the department is reviewing proposals submitted by other security providers during the recent bidding process.

Authorities still had not located the man described by Brown. The intruder was described as about 6 feet tall and wearing dark jeans, a gray-hooded sweatshirt and white, dirty sneakers, state police Maj. Steven O’Donnell said.

Brown, 37, of Warwick, found him in a vacant building as he investigated reports of suspicious activity on the campus.

He was carrying a 9 mm handgun. During the altercation, the intruder fell down a set of stairs and then climbed back up with a rusty knife in his hand, O’Donnell said.

Brown fired, and believed he had shot the man, but investigators did not find evidence of such an injury, O’Donnell said.

mreynold@projo.com