Within minutes there was a heavy police presence as San Diego County deputies streamed into the track and a helicopter was seen overhead.
The unidentified man was taken to Scripps Memorial Hospital La Jolla.
The racetrack tweeted less than an hour later that the situation has been contained and the concert was moving forward.
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Daniel Elizarraras, 22, from Escondido, was told that the show was sold out at around 6:40 p.m. on September 2, after which he got into an argument, according to the San Diego Sheriff's Homicide Unit.
There were 18,000 people on hand for the Summer Concert Series at the Del Mar Fairgrounds. After an argument ensued, Elizarraras pulled out a silver plated semi-automatic handgun and reportedly fired three shots in the air.
The man had been trying to buy a ticket to the concert featuring the rapper Sunday at the Del Mar Fairgrounds in San Diego, the department said in a statement. To our knowledge, no one else was injured.
His condition was not immediately available. Just half an hour after the shooting, and with the day's racing finished, the racecourse tweeted that the gangsta rap gig would go ahead as planned.
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Del Mar Thoroughbred Club said in a statement: "As is our special events protocol, substantial law enforcement and private security was on site in anticipation of the event".
Police are continuing to investigate the incident.
Del Mar's final day of racing will begin at 2 p.m. tomorrow as scheduled.
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