UPDATED | April 25, 2017 10:57 AM

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DALLAS (CBSDFW.COM) – There are still questions today about what prompted an employee at a Dallas business to kill his boss and then take his own life.

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Workers are returning to the building where hundreds were forced to evacuate Monday.

When people heard gunfire coming from a corner office they ran for cover. One visibly shaken person said, “The shots. They were so close. You could hear the shots.”

It was a very tense morning for people who worked at the high-rise office building just off the LBJ Freeway, near the High Five.

Sources tell CBS 11 News the shooter, Matthew Kempf, knew that when he arrived at work he was going to be fired from hospice and home health care company Dignity Team Health. According to police, Kempf, 60, went into a meeting room on the 7th floor, shot his female supervisor Lana Claudine Canada, and then shot himself.

Tuesday morning, police released information that Canada, 48, had just gotten married last month.

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As the sound of gunfire rang through the building just after 10:30 a.m., other employees locked their doors and took cover.

The Dallas Police Department SWAT Team went floor to floor and cleared everyone out.

Leo Garcia was one of many employees in the building who wasn’t sure what to do. “We finally made the decision, ‘okay, let’s go.’ So, we just ran out and the police officers were on the stairs waiting for people saying ‘go, go go.’”

Cleaning crews worked late into the night, trying to make sure the building could reopen today. Still, a boarded up window is a reminder of what happened.

Officers had to use a shotgun to break through the glass front office door. DPD assistant chief of investigations Randy Blankenbaker said that was the only shot that any officer fired during the incident.

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One police officer was cut by broken glass but no other employees were hurt.