PHOENIX -- One person was killed and five more were injured in a Wednesday shooting at a Phoenix office complex at 16th Street and Orangewood Avenue.
Another victim died Thursday night.
The suspect was identified as 70-year-old Arthur Douglas Harmon said Phoenix Police Sgt. Tommy Thompson. He disappeared after the shooting, last seen in a 2013 white Kia Optima.
Harmon was found dead of an apparent self-inflicted gunshot wound early Thursday in a Mesa shopping center parking lot.
There weapons were found at the scene, including a Springfield 1911 .45 caliber pistol, a Ruger .22 caliber pistol and a 1970's vintage Colt AR15 rifle.
According to Sgt. Tommy Thompson of the Phoenix Police Department, Harmon used the pistols in the office complex shooting, while the rifle was fired at the witness who followed him.
Phoenix police called the 16th Street shooting "not random."
Police, SWAT, fire and emergency crews arrived on the scene about 10:30 a.m.
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.
Businessman Steve Singer and his lawyer Mark Hummels were shot and killed. Singer died a few hours after the shooting. Hummels died Thursday night. He had been life support after surgery at John C. Lincoln Hospital.
Hummels was representing Singer in mediation at the time of the shooting.
Singer was CEO of Fusion Contract Centers Inc., a Scottsdale company named in a lawsuit filed by Harmon.
The company had hired him to refurbish office cubicles at two call centers in California, but a contract dispute arose.
Fusion says Harmon was paid nearly $30,000 under the $47,000 contract. But Fusion asked him to repay much of the money when it discovered that the cubicles could not be refurbished.
Harmon's lawsuit sought payment for the remainder of the contract, $20,000 in damages and reimbursement for storage fees for the cubicles and legal costs.
Police were present at a house at 28th Street at Acoma Drive, less than 10 miles from the shooting, around 12:30 p.m. About 4 p.m., officers moved on the home.
Witnesses to the crime reported hearing multiple shots. The three-story building went on lockdown and nearby buildings were evacuated.
A witness named Rob said he heard five or six gunshots and two people lying on the ground near the rear of the building.
Karen Greenhow was with a group of people who hid in an IT equipment room in one of the second-floor offices.
"I heard two very loud noises. I thought maybe it was construction something had fallen, I didn't relate it to gunshots at the time. Then someone ran through the office and said there had been a shooting, that here had been a man with two guns."
Another witness, Kristie Wingel, was with Greenhow.
"The people in the front of the office started running to the back and we all hid in an IT closet," she said. "We were calling 911."
One witness, who identified herself as Becky Neher, said she heard the shots, but didn't realize there was an active shooter until she saw people running.
"We're on the second level and I saw some girls running out of the building below us."
Neher said herself, along with fellow employees, ensured the doors of their business were locked before proceeding to the rear of the office. When they looked out the window, the employees saw two men lying on the ground.
All schools in the nearby Madison School District were placed on lockdown as a precaution, but all schools were later released with no incident.
16th Street was closed for hours while police carried out their investigation. It was reopened about 5:20 p.m.
The Associated Press contributed to this report.