The victim was beaten Wednesday night at the Yosemite Recreation Center. Police say the man was jogging when four teens robbed him of his MP3 player, and then beat him over the head with their skateboards.
The victim was able to make it to a neighbor's house where he got help.
"He was actually hard to recognize because he was just covered in blood, with lacerations on his head that were just still bleeding," said the victim's neighbor, Michael Larsen.
Police say the suspects are not gang members, but they believe they are members of a "tagging" graffiti crew. Graffiti is painted on buildings and benches at Yosemite Recreation Center.
For some of the residents who use the park at night, their sense of security is in question.
If you have information about the attack, you're asked to call the LAPD at (877) LAPD-24-7.