Story highlights One of three shooting victims dies of injuries, Phoenix police say

Other two victims have non-life-threatening injuries, police say

Police identify suspect as Arthur Douglas Harmon, 70, last seen in a white Kia

Phoenix police were searching Wednesday for a 70-year-old man suspected in the shooting of three people, one of whom died, in an office building.

Arthur Douglas Harmon had gone to the building to discuss "some type of litigation," Phoenix Police Public Information Officer Tommy Thompson told CNN affiliate KTVK

After the meeting, at about 10:30 a.m. (12:30 p.m. ET), Harmon shot Steven Singer, 48; a 43-year-old man who was in critical condition, and a 32-year-old woman, Thompson said.

The law firm of Osborn Maledon identified one of its attorneys, Mark Hummels, as one of the victims. He was involved in a client mediation when he was shot, the Phoenix firm said.

"We believe the two men were his targets," Thompson said. The woman, whose injury was not life-threatening, "just happened to be in the way when the shooting occurred."

Harmon then fled in a 2013 Kia Optima, Arizona license plate AVS-2052, he said. Harmon shot at a witness who was following him, Thompson said. "Anybody who contacts him needs to be aware that he is armed and dangerous," he said.

Two other people who were not shot were also taken to a hospital, one for "some other type of injury not related to gunfire," and the other "may have been related to stress," Thompson said.

Former astronaut Mark Kelly referred to the shooting during a Senate Judiciary Committee hearing in Washington on gun violence. "There's 50 or so police cars on the scene," he said.

Kelly and his wife, former Rep. Gabrielle Giffords, D-Arizona, this month launched Americans for Responsible Solutions, which seeks to raise money to counter the influence of the gun lobby.

Two years ago, Giffords was shot in the head by a gunman in a parking lot in Tucson.