22-year-old Daniel Elizarraras wanted to buy a ticket to Rapper Ice Cube's concert, but no more tickets were available, San Diego County sheriff's spokeswoman Lt. Karen Stubkjaer said.
In another video the person filming can be heard saying, "He shot him, he shot him", while people run away from the gunshots. Track announcer Trevor Denman said the concert would be shown on the large screen in the infield and on television monitors throughout the plant.
The race track later tweeted that the situation was contained, and the concert would go on as scheduled.
San Diego'sFOX 5 reported that a San Diego Sheriff's Department deputy had shot a suspect near the racetrack entrance.
"An argument ensued at the gate and nearby deputies responded".
Elizarraras proceeded to pull out "a silver-plated semi-automatic handgun", police said, firing several shots into the crowd outside the Del Mar racetrack. When he did not cease his aggression after the tasing, the sheriffs opened fire and wounded the suspect, according to witnesses.
No other details were immediately known.
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". To our knowledge, no one else was injured.
"We take consolation in the fact that no patrons, officers or security personnel were injured in the incident", the statement said.
The shooting, which occurred during the final race of the day, created a chaotic scene at the venue.
Ambulances and helicopters were also seen shortly after the shooting.