Mark Hummels, a lawyer who was wounded after a gunman opened fire following a dispute at an office space, has died from his injuries.  Hummels is the second fatality after Arthur Harmon, a landscaper in the Phoenix suburb of Mesa, opened fire. Hummels, 43, was the second of three people hit by Harmon. Steve Singer, 48, also died hours after the attack.

Hummels worked with the Phoenix law firm Osborn Maledon. Colleagues of Hummels described him as a smart, competent and decent man who was a rising star in his profession and dedicated to his wife, 9-year-old daughter and 7-year-old son, the Associated Press reports.

News reports said that police indicated that Harmon got into a dispute, apparently at the end of a mediation session over a lawsuit he filed last April. The argument heightened to the point where Harmon pulled a gun out and opened fire. The shooting occurred at about 10:30 a.m. The gunfire that ensued caused workers throughout the complex to lock their office doors to their offices; SWAT officers searched the building.

Steve Singer, 48, a father of two and CEO of Scottsdale-based Fusion Contact Centers LLC, was the first fatality, and died after the shooting.

According to the USA Today, 32-year-old woman, Nichole Hampton, 32, of Waddell, Ariz., who had gone outside to take pictures and was caught in gunfire near the building entrance. She suffered from hand injuries.

Hummels, who died on Thursday night, focused on business disputes, real estate litigation and malpractice defense, his publicist Athia Hardt told The Associated Press early Friday. He was also a reporter for the Albuquerque Journal and Santa Fe New Mexican before he left to go to law school in 2001.