According to a law enforcement document, Arambula was arrested Monday afternoon on the charge, which is a misdemeanor offense.
Fresno Police Chief Jerry Dyer tells Action News that the arrest came after Child Protective Services was called out to Dailey Elementary Charter School in Central Fresno on Monday afternoon after a child was found to have an injury.
VIDEO: Chief Dyer explains what led to the arrest of Assemblyman Arambula
After interviewing the child, Child Protective Services asked the Fresno Police Department to come to the campus. After seeing the evidence of the child's injuries and reviewing the child's statement, police determined that Joaquin Arambula was responsible for the injury.
Chief Dyer says that based on the evidence and the statement of the child, that the incident occurred at about 8:30 pm on Sunday.
Police called the Arambula home and reached Joaquin's wife, who came to the school. Joaquin also came to the school later with an attorney.
On the advice of his attorney, Arambula refused to give Fresno Police a statement.
Joaquin Arambula was taken to Fresno Police Headquarters to be processed and cited for the crime and he was immediately released after promising to appear in court.
Chief Dyer says that the law prohibits the Fresno Police Department from releasing the identity of the victim.
When asked for a comment on the charge, the Assemblyman's office released a statement that read: "Joaquin is a committed father who wants what is best for his children. He is fully supportive of the process, which will show he is a loving and nurturing father."
Chief Dyer says that the injured child is no longer in an environment where there is any contact with Joaquin Arambula and has been placed with a relative. The chief also says that Arambula does not pose a risk to any other children.
For this type of child abuse charge, Arambula could face up to one year in jail if he is convicted.
Legal Analyst Tony Capozzi says child abuse cases ultimately end up becoming a judgment call over what is overbearing punishment.
"This is filed as a misdemeanor, that says something within itself. that's not as serious as you think it may be," Capozzi said. "In this case i question if it's going to go a whole lot further than the court process, the question now is if the DA will even file charges."
If they do -- Capozzi says it won't be surprising to see the case used as ammunition by more political opponents.
Already, the chairman of the Fresno County Republican Party is asking for Arambula to step down.
"California State Assembly Speaker, Anthony Rendon, should ask for Joaquin Arambula's resignation due to the egregious nature of these charges," chairman Fred Vanderhoof said in a statement.
Arambula was first elected to the State Assembly in an April 2016 special election to replace former Assemblyman Henry Perea, who resigned to work for the pharmaceutical industry.