DELHI, California (STPNS) -- Students remained on lock down throughout their school day on Monday. Students were released at the end of the school day as officers completed classroom checks.

A backpack containing three handguns and an SKS rifle near it were discovered across Merced Avenue from the Delhi High School baseball field. The person who found it has been identified only as someone scavenging for cans.

"We erred on the side of caution," Sheriff Mark Pazin reported at a press conference Monday afternoon.

The person who discovered the backpack reported it to a school maintenance worker who then informed School Resource Officer Joey Cardenas, according to Pazin. The Sheriff's Department opted to lock down the school to make sure no additional weapons were in the area. Originally, school district officials reported that Deputy Cardenas discovered the backpack.

Sheriff Pazin also reported that graffiti was found on a school building that depicted a person with a bullet wound to the forehead. That graffiti appeared over the weekend and combined with the discovery of the firearms, extra caution was taken. Pazin also noted that today being the anniversary of the terrorist attacks on the east coast five years ago raised additional concern.

"It looked like a recipe for disaster," Pazin said.

No arrests have been made and not everything has yet been ruled out. Pazin indicated that investigating officers will continue to work into the night on trying to put all of the pieces of this puzzle together. After the perimeter search of the entire Delhi Educational Park, students were moved into a central location as officers methodically searched each classroom. The search of the school and surrounding area turned up nothing.

"We've done everything we can," Pazin said. "We are relieved nothing else was found."

The Livingston Police Department, Atwater Police Department and California Highway Patrol assisted throughout the day.

In addition to the firearms, a notebook and a reading book at an estimated fourth to sixth grade reading level were discovered in the backpack.

Pazin said that the first theory is that something was going to be amiss, but they have not been able to rule out the possibility that the backpack was dumped for some reason. One of the firearms was reported missing in Garden Grove about one year ago, Pazin said. The investigation will continue and Pazin has assured the Delhi community that extra precautions will be taken Tuesday. Additional patrols will be on hand in Delhi. Pazin credited the tremendous partnership between the Sheriff's Department and the Delhi community with assisting in today's efforts.

That partnership is evidenced by the role Deputy Cardenas plays in the community. In addition to his daily duties as the school resource officer, Cardenas has been instrumental in the summer block parties that are put on with the help of the Delhi Volunteer Fire Department, Merced County Sheriff's Explorers and added this year, local pastors and the California Highway Patrol.