The gunfire rang out on Sunday night as former Jamaican prime minister and current JLP leader Andrew Holness was finishing a nearly hour long speech in Sam Sharpe Square, NBC news cited Jamaican newspaper The Gleaner as reportig on Monday.
Security officers rushed the stage to remove Holness.
A photo posted on the JLP's Facebook page before the shooting showed people packed into the square.
The JLP called the shooting a "barefaced and heartless attack on the democratic process" in a post on Facebook. The party said Holness was in shock and expressing "heartfelt sadness" at the shooting during the party's official campaign launch ahead of Feb. 25 parliamentary elections.
"Tonight my heart is heavy, I am terribly saddened by tonight's unspeakable incident and my sympathy goes out to the families of those who lost their lives, and my prayers are with those who were injured," Holness said in a statement issued by the party.
Jamaica Labour Party General Secretary Horace Chang immediately wrote rival People's National Party leaders and election officials to request a meeting to discuss the shooting, the party said.
Holness called on JLP supporters not to interfere with authorities investigating the shooting.