At least 10 boys were victims of a former school instructional assistant who assaulted students and created child pornography on school grounds, the Charles County Sheriff said Monday.

The aide, 30-year-old Carlos Deangelo Bell, of Waldorf, Maryland, has told law enforcement that he is HIV positive, Sheriff Troy Berry said.

Berry added that law enforcement is not aware of any victim who has contracted HIV, but that more testing will happen.

The victims were all boys, "mostly middle schoolers and pre-adolescent students," Berry said. He added that there may be more victims.

He urged families to talk to their children if they have had any contact with Bell. Charles County and the FBI have set up a phone line for anyone who may have been a victim; that number is 800-CALL-FBI.

Seven of the at least 10 victims have been identified, authorities said.

Bell was identified after a parent noticed suspicious text messages on a child's phone in December, Berry said. At that time, Bell was removed from Charles County Public Schools, said Charles County school Superintendent Kimberly Hill. Law enforcement launched an investigation.

Last week, investigators notified the Charles County Sheriff's Office that child pornography had been found on Bell's personal electronic devices, Berry said, including graphic images of Bell sexually assaulting children.

One of the videos appears to show Bell having sex with a child inside a classroom at Benjamin Stoddert Middle School in Waldorf, Berry said.

"Some of the crimes appear to have been committed on school property, and others at his home in Waldorf," Berry said.

Law enforcement and schools in Charles County, Maryland, detail charges against a school aide who is accused of assaulting students and creating child pornography. Some of the assaults occurred on school grounds.

Bell was arrested Friday; the same day, a Charles County grand jury indicted him on two counts of second-degree assault and three counts of production of child pornography. He is being held without bond.

Additional charges are likely, said Tony Covington, state's attorney for Charles County.

"The facts that buttress those charges are chock-full of allegations of sexual assault," he said.

Bell had worked as an instructional assistant at Stoddert Middle School, which included working with some students with special needs. He also had worked as a track coach at La Plata High School.

He had worked for Charles County schools since fall 2014. He also had worked at J.P. Ryon Elementary School in Waldorf and had been a track coach at Maurice J. McDonough High School in Pomfret.

Bell has not worked for Charles County Public Schools since Dec. 22, 2016, Hill said.

"In an organization that is all about children, these allegations are horrifying," Hill said. "To our parents and our community, who put their faith and trust in us to safeguard their children, I apologize on behalf of Charles County Public Schools. Student safety is job one, and clearly we have work to do to make sure that this will never happen again."

The victims will get support and counseling, Hill said, and the school district will launch a "comprehensive and transparent" review of safety protocols and the curriculum around sexual harassment.

Covington said the delay between the report of an inappropriate text and the discovery of the child pornography, by Maryland State Police, was not unusual. There is no evidence that student who received the text had any physical contact with Bell.

"Frankly, I am not sure there is a faster track," Covington said. "I will tell you that it takes about eight months on any case when you are talking about computers. In a new day and age, computers and other devices are used all the time in crime."

Covington added, "The reality is, they don't have the resources to get it done more quickly."