LARGO — A man distraught because he suspected his wife was having an affair walked into a glass-walled office complex Wednesday morning and began firing a semiautomatic handgun, ending by shooting himself in the abdomen, police said.

Gunman Fred Michael Sumner, a 52-year-old Largo resident, survived and was airlifted to a local hospital for treatment after the outburst at his wife's workplace. No one else was injured, police said.

The incident sent fear and confusion rippling through the multiple businesses that occupy Bayview Pavilion, a three-story office building at 15550 Lightwave Drive, near the intersection of Roosevelt Boulevard and 49th Street.

In the aftermath, workers described the sound of gun blasts reaching them at their desks as they began the workday.

"I was just trying to survive. That's it," said David Davis, 27, who works for Matrix Medical Network, a company that markets health care plans, on the first floor of the complex. "We had a lot of people who dropped down in their cubicles. I just ran for cover."

Davis said he and his roughly 200 co-workers faced a potentially dire scenario, since the office's only exit is through the lobby, where Sumner was firing his gun.

"You don't think a situation like that is going to happen at your job," he said. "The most scary thing is that there's only one way out. "

Alexandria Morgan, 23, works for Clarity Services Inc., a credit bureau on the third floor of the complex. She said she was one of those who called authorities when she heard gunfire Wednesday.

"We heard gunshots, and I called 911 and ran for the stairwell," Morgan said. "It was very scary … none of us here have any idea what's going on."

Largo police responded to the shooting after receiving multiple 911 calls at 9:28 a.m. Wednesday. According to Largo police Lt. Mike Loux, witnesses said Sumner walked into the lobby, said something indistinct, then removed the gun from his waistband. He fired four or five shots, shattering the windows and doors.

He then shot himself, Loux said. Sumner did not threaten or aim his gun at anyone else in the lobby. He was booked into the Pinellas County Jail on Wednesday on charges of criminal mischief and shooting in an occupied structure and was being held Wednesday evening on $25,000 bail.

The three-story office complex is home to at least four businesses, including Matrix Medical Network, Clarity Services Inc., Universal American Mortgage Co. and Inuvo Inc., a technology and marketing firm. Police said Sumner's wife works in the building, but was not there Wednesday morning. She was located by authorities unharmed.

While police would not disclose her identity, relatives said she is Marcie Sumner, 32. The couple lives together at an apartment complex in Largo, according to public records.

Police did not disclose the details of Sumner's suspicions about his wife or why he chose to bring a gun to her office building.

"I just can't hardly believe that this has taken place," said Fred Sumner's cousin, Steve Hobbs, a resident of Lenoir City, Tenn. Hobbs said his cousin, with whom he is close, is a guitar-strumming recreational fisherman who enjoys spending time with his large extended family. Fred Sumner has worked as a trucker and bus driver, Hobbs said.

"I know people can just snap sometimes, and I have a feeling that's what happened to him," Hobbs said. He said he was unaware of any marital discord between the Sumners.

News researcher Carolyn Edds contributed to this report. Peter Jamison can be reached at pjamison@tampabay.com or (727) 445-4157.