Mesa security at Mesa Riverview reportedly saw the car and called Mesa Police.

A gunman opened fire outside a Phoenix office building near 16th Street and Glendale on Wednesday, killing one person and wounding two. He remains at large.

The suspect's name is Arthur Harmon, 70, and he was last seen driving away from the scene in a rental car, a white 2013 Kia Optima, Arizona plate AVS-2052.

"We believe these individuals were involved in some type of meeting involving litigation, and that's when the shooting occurred," said Phoenix Police Sgt. Tommy Thompson."We believe he was alone, that this was not a random incident, and we want to get him into custody."

Police believe that Harmon got in a confrontation outside of the office with 48-year-old Steve Singer and 43-year-old Mark Hummels after the meeting, and he shot them. 32-year-old Nichole Hampton was injured by gunfire in the process, and she is believed to have been an unintended victim. Hampton was shot in the hand and it shattered her wrist -- she was in the lobby when the gunman opened fire.

Singer worked as CEO of Fusion Contact Centers LLC. Harmon apparently filed a lawsuit against Singer's company, and attorney Mark Hummels was representing Fusion. Singer was killed, and Hummels was wounded and remains in critical condition.

Harmon fled the scene in the Kia, and as he was fleeing, a witness followed him. Harmon fired a shot in his direction -- that person was not hit. Two others were hospitalized for non-gunshot related reasons.

A spokesperson from Osborn Maledon law office issued this statement, in part: "Our partner, Mark Hummels, was representing a client in a mediation today when he was shot... Our concern right now is for Mark and his family."

Fusion had hired Harmon to refurbish office cubicles at two call centers in California, but a contract dispute arose.

Fusion said Harmon was paid nearly $30,000 under the $47,000 contract but asked him to repay much of the money when the company discovered that the cubicles could not be refurbished, according to the documents.

Harmon argued Fusion hung him out to dry by telling him to remove and store 206 "worthless" work stations after the mix-up was discovered. Harmon said Fusion then told him that the company decided to use a competitor.

Harmon's lawsuit had sought payment for the remainder of the contract, $20,000 in damages and reimbursement for storage fees and legal costs.

Court documents show there were allegations he fraudulently transferred the title of his house.

Gunfire erupted about 10:30 a.m. Wednesday prompted terrified workers throughout the complex to lock the doors to their offices and hide far from the windows.

About 30 minutes after shots broke out, SWAT officers entered the building and paramedics carried out the victims. Nearby Madison Middle School was on lockdown until 2:10 p.m.

A SWAT team later surrounded a house 7 miles from the shooting scene. There, officers questioned Harmon's adult son, Phoenix Police Sgt. Steve Martos said.

The suspect's son did not give police permission to search the house, so officers had to wait for a search warrant to enter, about 3:45 p.m. However, Harmon was not inside. Detectives were collecting evidence all night and believe they have some information that will help them locate him.

Debbie Carmichael is a nurse who works in the bottom floor of the office building where the shooting occurred.

"I've got a lot of healing that needs to go on today because of what my employees saw," said Carmichael. "But, what I saw was a lot of good people. I was there with the victims...you know, as a nurse that's what you do, you go and you take care of those who need you."

Navika Sood, assistant director of nursing at First at Home Health Services, said she heard a handful of loud popping noises Wednesday morning. She said she and her co-workers locked the entrances to their office and gathered in one area away from the windows.

"Everyone was just scared, honestly, just scared," she said.

Vannessa Brogan, who works in sales support in an insurance business in the three-story complex, said she heard a loud bang that she thought at first was from somebody working in or near the building. She said others at the business thought they heard multiple loud noises.

She said people locked themselves in offices until authorities evacuated the central Phoenix building that houses insurance, medical and law offices.

Later Wednesday, police found Harmon's cell phone dumped near 40th Street and Shea. He may be carrying two weapons, including a handgun. He is considered "armed and very dangerous."