A body found in bush in an Arizona suburb has been positively identified as the man who killed a company CEO and critically wounded a lawyer a day earlier, police say.

A landscaper found the body of Arthur Douglas Harmon, 70. He died of an apparent self-inflicted gunshot wound, and a handgun was also found, police said.

Nearby in a parking lot was a rented Kia Optima sedan he drove to the shooting scene, authorities said.

Harmon drew a gun and shot both men at the end of a mediation session on Thursday at an office building in north-central Phoenix, police said.

Steve Singer, 48, died hours later. Mark Hummels, 43, is in critical condition. A 32-year-old woman was also shot but suffered non-life threatening injuries.

"We believe the two men were the targets. It was not a random shooting," said Sergeant Tommy Thompson, a Phoenix police spokesman.

Harmon also shot at someone who tried to follow him to get his license plate number, authorities said.

"As he left the scene, an individual witness got in his own car and actually followed Harmon in his Optima, and he drove into a neighbourhood and Harmon actually got out of his car and shot at that witness," Thompson said.

Singer was the CEO of Fusion Contact Centers, which had hired Harmon to refurbish office cubicles at two call centres in California.

According to court documents, Harmon was scheduled to go to a law office in the building where the shooting took place for a settlement conference in a lawsuit he filed last April against Fusion.

The response to the shooting centred on the building - home to insurance, medical and law offices - but soon spread to a north-Phoenix home and a central-Phoenix high-rise office building where Hummels' office is located.

Special Weapons and Tactics teams and two armoured vehicles surrounded the house. Police served a search warrant to enter the house, which county property records show was sold by Harmon to his son last year for US$26,000.

For a time, officers used a megaphone to ask Harmon to surrender, believing he might be inside the home.

The shooting took place on the same day that hearings on legislation to address gun violence were convened in Washington, with former congresswoman Gabrielle Giffords testifying for stricter gun controls.

A gunman shot Giffords in the head during a shooting rampage in Tucson in January 2011.

- AP