One of the people killed in a Chicago law firm shooting Friday was an attorney with offices on the Big Island, authorities said.

Patent, trademark and copyright law attorney Michael R. McKenna, 58, of Chicago, had offices in Kailua, Kona. He also had two firms in Illinois — one in Chicago and a second in Northbrook.

No one was available for comment yesterday at McKenna's law offices on the Big Island. McKenna apparently is not related to car dealership owner Mike McKenna of O'ahu.

Chicago authorities said yesterday the 59-year-old gunman who fatally shot McKenna and two others in a law firm's high-rise offices felt cheated over an invention and had a vendetta against McKenna, the Chicago Tribune reported.

"We know he went there for Mr. McKenna, then he continued to shoot other people," said Chicago Police Superintendent Phil Cline.

Police identified the gunman as Joe Jackson, who was killed by police. They said Jackson forced a security guard at gunpoint to take him up to the 38th-floor law offices of Wood, Phillips, Katz, Clark & Mortimer, which specialize in intellectual property law.

He carried the revolver, a knife and hammer in a large manila envelope and chained the office doors behind him, police said.

Jackson told witnesses before he was shot that he had been cheated over a toilet he had invented for use in trucks.

His bullets sprayed the offices with blood and broken glass. One victim was left dead in a hallway, Cline said.

SWAT officers killed the gunman, shooting him in the face and chest with sniper rifles from about 45 yards away, after he grabbed a hostage, Cline said. Police made no attempt to negotiate with Jackson. The hostage was unharmed, police said.

"He had already shot four people. He had reloaded his gun," Cline said. There were 25 to 30 other people on the floor at the time.

The shooting at the 43-story Citigroup Center sent office workers fleeing. In addition to McKenna, those killed were Allen J. Hoover, 65, of Wilmette; and Paul Goodson, 78, of Chicago. The medical examiner said Jackson died of multiple gunshot wounds.

Colleagues told reporters Hoover was a partner at the firm, and McKenna was a patent attorney who rented space from the firm and also had offices in suburban Northbrook and in Hawai'i. Goodson worked part-time at the firm to sort mail and make deliveries.

Cline said Jackson had McKenna's business card in his pocket.

He also said Jackson had tried at least one other time on Friday to go up to the firm's offices but was turned away.

Jackson had three criminal offenses on his record, none of which were recent. In 1968 Jackson was arrested for unlawful possession of a weapon, and in 1977 he was arrested for stealing a car.

Police said McKenna's longtime paralegal, Ruth Zak Leib, 57, of Oak Park, was wounded. She was treated for a gunshot wound to the foot and released.

McKenna has a son who is a police officer in Chicago. The man was not among officers who went to the scene, Cline said.