SAN ANTONIO -

Castle Hills police continue to investigate a former assistant football coach at Antonian College Preparatory High School after he was fired for what school officials called "improper videoing of students."

In a letter sent home to parents, Antonian Principal Gilbert L. Saenz said Larry Ruiz, 28, was fired Wednesday after students reported Ruiz videotaping students in class with his personal cellphone. 

"He left his phone with the administration and they released it to us," said Castle Hills police Capt. Johnny Siemens. "When they reached out to us with possible criminal activity, our detectives ... obtained a warrant to search that phone."

According to Saenz, Ruiz had only worked there for a few years and was a part-time football and track coach. 

He also was a substitute teacher. 

Saenz said Ruiz was substituting in sophomore- and junior-level classes Wednesday when two female students came forward and reported what seemed to be improper videoing of students.

"(In) a classroom setting, I can only imagine -- it being a uniformed school -- that there were skirts involved and improper video," said Siemens.

Siemens said he encourages parents to talk with their children about the case and to report any information that may seem relevant.

"I would advise any others to not hesitate (and) to always reach out to a trusted faculty member, coach, friend, administration, counselor, employee -- make that report and let the authorities take over from there," said Siemens.

Castle Hills police officials said they could not comment on Ruiz's criminal past, if any. They say he has not been arrested, but he is being investigated for improper video recording, a state felony, and if a person is convicted on that charge, he or she could face between two to 10 years in prison. 

For a list of recent stories Mariza Mendoza has done, click here.