A 52-year-old man is in custody after barricading himself with a gun at the Stellantis Sterling Heights Assembly Plant on Saturday afternoon, according to police and the automaker.

According to Sterling Heights Police Captain Mario Bastianelli, officers responded to a 911 call at 4:30 p.m. reporting a man armed with a handgun and possibly undergoing a mental health crisis inside the plant.

Officers arrived on the scene and were able to locate the man in the center of the plant and contained him in a small area. Workers in the plant were able to safely evacuate, authorities said.

“After about a three-hour standoff we were able to convince him to come out and he was taken into custody peacefully,” Bastianelli said.

Police confirmed no shots were fired by police or the gunman, who is a Stellantis employee, and no one was injured during the standoff.

“The plant was shut down for a few hours but everyone was safe which is the best outcome we could have in this situation,” Bastianelli said.

He said Stellantis was working on reopening the plant as of 7:30 p.m., about 20 minutes after the gunman was arrested.

Police are uncertain as to why the employee brought a gun to the plant.

“When the call came in, the caller said the man was armed and possibly hallucinating so we don’t know if he is under the influence of something or if it is a mental health situation but we are still working that out right now,” said Bastianelli. “If there is a need, we will get him medical care but we don’t know his status right now.”

Police did not identify the gunman and or how long he had worked at the Sterling Heights Assembly Plant.

The plant wasn’t operating on Saturday, and there was a “skeleton crew” of workers, according to Stellantis.

The plant is located along Van Dyke Avenue north of Metropolitan Parkway in Sterling Heights. Several SHAP employees reported Saturday on social media being told to exit the plant due to a person with a gun in the plant.

Officials on Sunday said the incident remains under investigation.