The victim, identified as 43-year-old Mark Hummels, is the second person to die in the workplace shooting which took place early Wednesday.
Arthur Douglas Harmon, 70, opened fire at a law office in north-central Phoenix at the end of a mediation session over a lawsuit he filed last April. The gunman intially killed 48-year-old Steve Singer, and wounded Hummels and a 32-year-old woman.
Singer was the chief executive of Scottsdale-based Fusion Contract Centers LLC. The company had reportedly hired Harmon to refurbish office cubicles at two call centers in California. A contract dispute arose during their affiliation.
Fusion had paid Harmon nearly 30,000 under a $47,000 contract. However, according to court documents, the company had asked Harmon to repay much of the money after discovering the cubicles couldn't be refurbished.
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 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.
The company countersued Harmon, protesting the sale of his home to his son for $26,000 and asking a judge to prevent Harmon from getting rid of other assets. Harmon said the company's claims that the home was fraudulently transferred to his son were unfounded.
A landscaper found Harmon's body hidden in bushes in the Phoenix suburb of Mesa on Thursday. The gunman was found dead of an apparent self-inflicted gunshot wound.
Hummels represented Fusion in the lawsuit and was in the building where the shooting took place for a settlement conference. The victim had been on life support after the attack but died Thursday night at a Phoenix hospital, a publicist for his law firm confirmed Friday.
Hummels leaves behind a wife, 9-year-old daughter and 7-year-old son.
The Associated Press contributed to this report.