The gunman who opened fire at an Orlando factory had planned to kill five of his former coworkers by singling them out and shooting them before turning the gun on himself, investigators confirmed on Tuesday.

John Robert Neumann Jr., 45, had at least one "negative relationship" with one of his former co-workers at Fiamma Inc., whom he singled out and gunned down Monday, Orange County Sheriff Jerry Demings said. Neumann, who later killed himself as responding officers were heading to the business, was an army veteran who was discharged in 1999. He was fired from the RV awning manufacturing company back in April.

Police had confronted Neumann once before at the factory, when he was accused of battering a co-worker in June 2014. The co-worker said Neumann punched him in the back of the head knocking him to the ground, according to the incident report. But the co-worker later said Neumann chased him and then hit him on the back of the head.

The co-worker, who had no visible injuries, stated "he had problems in the past with John but thought they were resolved," the sheriff's office incident report said.

No charges were filed in the 2014 incident after both men were interviewed. The co-worker was not among Monday's victims, Demings said. Aside from the 2014 incident, Neumann also had a criminal history "minor in nature," with arrests for possession of marijuana and DUI.

Neumann walked into Fiamma Inc. off Forsyth Road in Orange County about 8 a.m. Monday and opened fire, Demings said. Deputies arrived two minutes later after a woman called 911 from the tile business store across the street.

"All she kept saying was he was holding a gun and told her to get out," said. Yamaris Gomez, the tile store's owner.

Shelley Adams told The Associated Press her sister, Sheila McIntyre, called her from the building's bathroom during the shooting and was very upset. She kept repeating "My boss is dead. My boss is dead," Adams said.

Officials found three men and a woman dead at the scene. A fifth person, a man, was rushed to the hospital, where he was pronounced dead. Seven people survived the shooting.

The five victims were later identified as Robert Snyder, 69, Kevin Clark, 53, Brenda Montanez-Crespo, 44, Kevin Lawson, 46, and Jeffrey Roberts, 57.

Fiamma Inc. released a statement on Tuesday saying she was "heartbroken" by the deadly and tragic attack.

"The company is heartbroken following the unspeakable attack upon our loved ones and employees. In these dark hours we ask for thoughts and prayers for all the victims of this tragedy and their families.," the statement read.

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Officials believe Neumann was the only gunman and there was no indication he was going to carry out the attack, according to Demings. Neumann paused at least once to reload his gun and most of the victims were shot in the head and some of them suffered multiple gunshot wounds, Demings said.

"This violence is frustrating. The only way we have a fighting chance is to ask the public to report any suspicious activity," Demings said.

The FBI was on the scene assisting local police on the investigation, a spokesperson from the bureau told Fox News. But Demings said authorities could not "connect the incident to any global terrorism."

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Florida Gov. Rick Scott said in a statement that he has been briefed on the situation.

"Over the past year, the Orlando community has been challenged like never before," Scott said.

"Ann and I are praying for the families who lost loved ones today. I ask all Floridians to pray for the families impacted by this senseless act of violence. I will remain in contact with the Orlando law enforcement community throughout the day as more information is made available," the statement read.

The shooting comes a week before the one-year anniversary of the Pulse nightclub massacre, also in Orlando, where 49 people were fatally shot by Omar Mateen, an Islamic extremist.

Fox News' Kathleen Reuschle, Catherine Herridge and The Associated Press contributed to this report.