SAN DIEGO - After the rain stopped and the sun came out Wednesday, residents in San Diego heard three loud booms. Residents took to social media to discover what was causing such a loud boom that some houses shook, but no answers were given, just speculations.

According to Duval County sheriff officials, sheriff deputies and game warden officers went out Wednesday to find the cause of such booms and ended at a ranch on County Road 103.

The agents located a group of people target practicing inside a caliche pit using rifles and tannerite exploding targets, said Patrol Lt. Johnny Perez with the Duval County Sheriff's Office.

Tannerite is a binary explosive targets used for firearm practice and sold in a kit form. The user mixes two chemicals, normally oxidizers and an aluminum powder, into a large or small capsule before shooting at it. 

When the tannerite capsule is shot at the explosive can be heard for miles.

Perez said the group target practicing are not violating any laws since they are in a secure and safe environment outside city limits and away from residential property.