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

No one was available for comment today at McKenna's law offices on the Big Island. McKenna is apparently no relation to car dealership owner Mike McKenna, of O'ahu.

Chicago authorities said today 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.

"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 specialized in intellectual property and patents.

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.

He was holding a hostage at gunpoint Friday when SWAT officers shot him from about 45 yards away, police said. There were no negotiations and 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 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.