"While we do not believe that students and staff were in any kind of imminent danger, as a precaution the campus had increased police presence and maintained a higher level of security at the school until the Corpus Christi Police Department gave us an 'all clear' at 10.30am," the district said in a statement.
Officers also went to the house of the student and a 30-year-old man was arrested and charged with making a firearm accessible to children and abandoning or endangering a child, police said.
Meanwhile, on Monday, a 7-year-old child was allegedly found to have a handgun, as well as ammunition, in their backpack at Cochise Elementary School in Bowie, Arizona, Huff Post reports.
Sheriff's deputies were called to the school and the child's parents were contacted. The child's father then reportedly checked on his guns and found a second weapon also missing. This was then allegedly discovered in the school office, where the child allegedly hid it while waiting for authorities to arrive, AFP reports.
"The parents were interviewed and advised that the weapons had been placed in what they believed to be a secure location away from the children after a recent camping trip," the sheriff's office said in a statement.
A spokeswoman for the sheriff's office said it was unlikely the child's parents would face charges but the incident remains under investigation.
The child now faces disciplinary proceedings under laws for dealing with juveniles.
Guns most common cause of death for US children
So far this year in the US, there have been at least 181 unintentional shootings by children, resulting in 77 deaths and 115 injuries, according to a count by Everytown for Gun Safety, a gun violence prevention organisation.
There are almost 400 million guns in circulation in the US – more than its population of 329 million.
Earlier this year, the US Centres for Disease Control and Prevention (CDC) revealed that gun deaths are the number one cause of death for American children and teenagers (up to the age of 19).
Just one month after the findings were released, one of America's deadliest school shootings took place, when 19 students and two teachers were killed at Robb Elementary School in Uvalde, Texas.
Following the incidents this week, police urged people to securely store their firearms, saying guns should be unloaded, trigger locked and locked in a gun safe or pistol box, with ammunition locked separately. Keys should also be placed out of children's reach.
In Texas, officials said: "We can never underestimate the role that all students, parents, and teachers play in keeping our schools safe and contributing to the overall success."
