A concertgoer was beaten by security guards during B.o.B’s set in Sacramento Sunday, and police don’t plan to investigate unless the victim files a formal complaint.  

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TMZ obtained footage of the unidentified male throwing the first punch at a security guard. Several other guards swarm, punching him before he’s hauled over a metal barrier — presumably so the crowd won’t see the rest of the beating. He's later handcuffed. 

The security guard that he originally swung on punches at the man in the face and head as he’s being walked out of the venue. 

After the show, the reported owner of the security company posted a Facebook message about the overall “great job” the team of 104 guards, 50 cops, horse and gang units, and parole agents did in controlling the crowd of 20,000.  

The concert was put on by radio station 102.5 KSFM and featured a roster that included Sage the Gemini, Tinashe and Big Sean. 

(Photo: Kevin Winter/Getty Images For 102.7 KIIS FM's Wango Tango)