A gunman who killed a woman before being fatally shot by a security guard at Citibank’s sprawling office complex in Tampa targeted the campus because he was angry over a $2,500 debt collection, a sheriff said Thursday.

About three hours before Wednesday’s shooting, Jacob Pearson called an attorney affiliated with Citibank and threatened violence, Hillsborough County Sheriff Chad Chronister told a news conference.

On the phone, Pearson demanded that the lawyer cancel a court hearing over Pearson’s unpaid credit card debt “unless you want me to go over there with my AR-15, my bulletproof vest and my insanity,” Chronister said.

The sheriff said Pearson, 35, had no criminal history. Pearson’s father, Richard Pearson, told The Associated Press that he had never seen an indication that his son was capable of carrying out a violent shooting.

Gunman targeted Citibank, but had ‘zero connection’ to the victim

The attack unfolded as many of the 3,200 employees at Citibank’s campus in suburban Tampa were eating lunch.

Pearson drove from his home in Orlando to Tampa, about 90 miles (144 kilometers) away, crashed his car through a fence at the campus and plowed into a courtyard where employees were eating lunch, Chronister said.

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The sheriff said Pearson got out of his car with a rifle and shot the first employee he saw. His rifle jammed after three shots, he said, and the gunman then retrieved a handgun from his car and again shot the same person, who died.

She was identified as 41-year-old Leanne Selman, who worked in human resources.

Selman had worked for Citibank for nine years and was “a beloved employee,” said Ed Skyler, spokesman for Citibank parent Citigroup. The sheriff said there was “zero connection” between Selman and her killer.

“He was there intent on one purpose, and that purpose was to hunt any human being he could find and kill them,” Chronister said.

As employees scattered to flee the gunfire, Pearson entered the building and walked through a cafeteria. An executive who is part of Citibank’s armed security team shot the gunman five times before he could hurt anyone else. Pearson was pronounced dead at a hospital.

The violence could have been far worse, the sheriff said. Pearson brought 90 rounds of ammunition to the campus, he said, but fired just 15 times before he was stopped.

No one else was shot, the sheriff said. Four people were treated at a hospital for minor injuries from fleeing and medical concerns such as chest pains.

Selman’s father declined to comment when reached by phone Thursday.