You can get it scanned for microchip at Petsmart or veterinarian for free.
Post it in the shelter phshelter.com as found, this increases the chance to find the owner. The shelter is the first place they check.
Post it on other lost and found social media such Pawboost, Nextdoor or Riverside - Moreno Valley Matters.
If claim please request proof of ownership such veterinarian records, pictures or to identify specific marks or characteristics of the pet.
Thank you for keeping it safe, he must miss his family. It might take days to hear from an owner, many don't have social media and will look for it at shelter, please make sure to report it as found so you can get contacted by the owner.