Cincinnati, OH – Authorities have announced that police stopped an active shooter on Thursday when they engaged him in a gunfight.

They added that man who opened fire in the lobby of the Fifth Third Center in downtown Cincinnati’s Fountain Square on Thursday had a checkered past that pointed to mental health problems.

Omar Perez, 29, fatally shot three people and wounded two more shortly after 9 a.m. on Sept. 6, before he was killed during a brief gun battle with police officers, the Cincinnati Enquirer reported.

Witnesses said Perez was wearing a business suit and carrying a briefcase when his rampage began.

Cincinnati Police Chief Eliot Isaac said the gunman used a 9mm handgun and was carrying hundreds of additional rounds of ammunition.

"This could have been a bloodbath beyond imagination," Hamilton County Prosecutor Joe Deters said at a press briefing on Thursday afternoon.

Chief Isaac said Perez entered the building in the center of downtown through the loading dock and began shooting right away, the Cincinnati Enquirer reported.

"He proceeded to the lobby, where several of our officers engaged him," the chief said. "There were gunshots exchanged."

"It's a very horrific situation,” he said.

Chief Isaac said all of the shooting took place in the lobby of the building which is home to Fifth Third Bank's corporate headquarters.

He said the shooter acted alone and investigators did not believe he had any connection to the bank or any of the other businesses located in the prominent building, FOX News reported.

Police responded immediately, and officers fired some of their first shots through the glass windows in order to get to the gunman, the chief told reporters at a briefing on Thursday.

"It could have been a lot worse. People in this town should just thank a cop when they see them, because what they did today was just unbelievable," Deters said.

Three or four officers fired at Perez. No police were injured. Perez was fatally shot during the gun battle, the Cincinnati Enquirer reported.

Chief Isaac said that Perez was acting alone when he murdered 64-year-old Richard Newcomer, 25-year-old Pruthvi Raj Kandepi, and 48-year-old Luis Felipe Calderón, ABC News reported.

Police have said they believe the handgun Perez used for his rampage was legally purchased, FOX News reported.

A SWAT team searched Perez’s home in North Bend on Thursday afternoon but said they found nothing of interest to the investigation.

But Perez’s police record and history of filing lawsuits against MSNBC tell a story of a man who may have suffered from mental illness.

FOX News reported that Perez had an extensive criminal history in southeast Florida with charges ranging from marijuana possession to traffic violations.

He was arrested and charged with trespassing in 2014 after he was fired from his job at a water sports company and refused to leave the premises.

The police report said that when officers responded to the business, they found Perez in front, stretched out on the ground smoking a cigar, the Cincinnati Enquirer reported. He began crying when police arrived.

"The suspect appeared to be upset and disoriented. When I would ask the suspect questions but he would respond with strange answers,” the police report said, according to Cincinnati Enquirer. “The suspect mumbled something about the war and the economy, but for the most part talked about that he was upset that he was terminated.”

This year, Perez filed two separate lawsuits claiming MSNBC was spying on him, FOX News reported.

In January, he sued NBC Universal and TD Ameritrade Holding Corporation for $5.1 million in damages for emotional distress and “character assassination,” WCPO reported.

Perez claimed his cell phone and computer had been hacked and that "in a matter of four weeks (in spring 2017), ‘MSNBC' created a character, grandeur a persona, unmasked and assassinated the character through its slanderous commentaries,” FOX News reported.

When the suit was dismissed in June, Perez filed against the companies again.

He claimed that while he was watching MSNBC, they began broadcasting information about him and were trying track him down, according to WCPO.

In his lawsuit, Perez said that TD Ameritrade was working with MSNBC to tap into his phone and other electronic devices.

No motive is yet known for the shootings at the Fifth Third building, but authorities were continuing to investigate.