Before reaching out for help, try to determine if the cat is tame or feral.
If he's friendly, he's probably someone's pet that just got lost. Try taking photos of the cat and posting on Nextdoor.com. If you're able to get the cat into a carrier and take him to a nearby veterinarian's office, they can scan for a microchip (for free) to find the owner's contact information.
If the cat isn't friendly, check to see if the top corner of one of his ears has been cut off. When Trap-Neuter-Return (TNR) is performed on community cats (strays and ferals), they are "ear-tipped" so everyone can see that they've already been fixed.
If the cat is not ear-tipped, then you've either found a pet cat who's so scared that he's acting unfriendly or a community cat who still needs to be fixed. Getting community cats spayed and neutered is vital in reducing overcrowding at shelters and moving Los Angeles towards being a No Kill city. To do your part in achieving No Kill, please go to the FixNation website to find out how you can borrow a trap and get that kitty fixed, at no cost to you!