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A Pennsylvania educator was placed on leave after school administrators learned of his involvement in last week's protest in Washington that ended with the Capitol being breached by thousands of Trump supporters.

In a Jan. 7 letter to parents and staff, Allentown School District Superintendent Thomas Parker said the unidentified teacher will remain on temporary leave until the completion of a formal investigation. 

"The chaos that took place in the nation's capital yesterday was deeply troubling and acknowledge that these actions have caused immense pain in our community," he wrote. "Yesterday's events have added to the confusion and uncertainty our students are experiencing during this unprecedented time."

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An American flag flies at half-staff in remembrance of U.S. Capitol Police Officer Brian Sicknick above the Capitol Building in Washington on Friday. A Pennsylvania teacher has been put on leave pending an investigation into his involvement in the protest before the riot in the Capitol. (AP Photo/Patrick Semansky)

An American flag flies at half-staff in remembrance of U.S. Capitol Police Officer Brian Sicknick above the Capitol Building in Washington on Friday. A Pennsylvania teacher has been put on leave pending an investigation into his involvement in the protest before the riot in the Capitol. (AP Photo/Patrick Semansky)

The letter doesn't specify the teacher's school or the extent of his involvement Wednesday.  

Parker reminded district staff members to "think carefully" about what they post online, and how it could impact students and the community. 

"While we all have the right to express ourselves, it is important to do so respectfully. We ask the same of our students and families," he wrote. "We understand that many members of our community are upset by what happened. At the same time, the district has an obligation to uphold the First Amendment rights of our staff and students."

Inquiries to the district from Fox News were not returned. School Board President Nancy Wilt told Fox News "the matter remains under investigation and it is ASD Board standard procedure to not comment on personnel matters."

Messages to the district were not returned. 

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Several people caught storming the U.S. Capitol have been either terminated by their employers or placed on leave. A Chicago-area tech CEO said his involvement in the riot was the "single worst personal decision" of his life. He was eventually fired.

A New York man was suspended from his transportation job without pay after he was captured in images inside the Capitol.