Matthew P. Gagat, 47, is charged with open lewdness, court records show.
A witness called police to the park late on June 27 and described seeing a man who "appeared to be touching himself," police wrote in the affidavit. In a written statement, the witness said the man was "masturbating as he stared at her across the river," according to the documents.
Gagat was found in the same area of the park and matched the witness's description, authorities said.
He is listed as a fifth-grade teacher on the Haverford Township School District website, and according to court records was released on a $10,000 bail for a separate indecent exposure incident in Horsham on March 3.
In a statement, school district administrators said they only learned of the charges against Gagat on Monday, July 22.
"First and foremost, we understand and share in the concern this news causes, and the desire for more information and for a meaningful response from the school district," wrote Superintendent Maureen Reusche.
"We will do our very best to provide as much accurate information, context, and support as soon as possible."
"The challenge for a school system in these moments is to appropriately address our community's concerns while maintaining the procedures — both in the criminal justice system and as a District employee — that the individual is entitled to under the law," she continued.
"As both processes evolve, we will do our best to share as much information as we can share, with sensitivity and transparency."
Gagat has a hearing scheduled for the Montgomery County charges on Aug. 19 and another for the Bucks County charges on Sept. 17, court records show.
Click here to follow Daily Voice Hellertown and receive free news updates.