A captain in the Bridgeport Police Department is on administrative leave for allegedly sending racist text messages about an African-American officer.

Capt. Mark Straubel was transferred out of the chief's office.

Straubel, who was promoted to captain in 2016, has played a big part in running the department, including writing grant applications.

The mayor's communications director told News 12 that a citizen's complaint was filed with Internal Affairs against Straubel by a retired police officer. An internal affairs investigation is underway.

"We need to understand. This is not a joke. This is not just an instance or a statement. This is racism. That will not be tolerated," says Rep. Charlie Stallworth. Stallworth is a local pastor and president of the Interdenominational Ministerial Alliance. The group has pushed for more diversity within the police department.

George Mintz, the president of the Greater Bridgeport NAACP, says he was alarmed to learn about the accusations.

"He appears to be the nicest guy. I think he did an excellent job of covering it, of keeping it under cover," he says.

The local chapter does question who was aware of the alleged behavior.

"This was something known within the police department for perhaps 60 days or more," says John Marshall Lee, communications director of the Greater Bridgeport NAACP.

The local chapter of the NAACP is also calling on the police chief to look at how deep the issue goes within the department.

"In light of the sensitive nature of the allegations, I took swift action and immediately sent the captain home and placed him on administrative leave," Chief Perez said in a statement. "I am assured by the Office of Internal Affairs that this matter will be fully and thoroughly investigated. If the allegations are found true and accurate, the captain will be appropriately disciplined."

Straubel will continue being paid while the investigation continues.