Ecuador presidential candidate Fernando Villavicencio was shot dead during a campaign event in northern Quito on Wednesday night, according to Reuters.
A suspect in the killing of Villavicencio later died from injuries sustained during a shootout, the attorney general's office said on Twitter.
"A suspect, who was injured during the shootout with security personnel, was apprehended and moved, badly injured, to the (attorney general's) unit in Quito. An ambulance from the fire department confirmed his death, the police are proceeding with collection of the cadaver," the attorney general's office said.
Villavicencio's party Movimiento Construye said on armed men attacked its Quito offices.
President Guillermo Lasso confirmed the murder on Twitter and wrote, "For his memory and his fight, I assure you that this crime will not remain unpunished. Organized crime have gone very far, but all the weight of the law will fall on them."
Lasso said he would host top security officials at an urgent meeting.
Videos on social media purportedly from the campaign event showed people taking cover and screaming as gunfire sounded.
According to opinion polls, Villavicencio's support was at 7.5%, ranking him fifth out of eight presidential candidates for the August 20 vote.
Villavicencio, from the Andean province of Chimborazo, was a former union member at state oil company Petroecuador and later a journalist who denounced alleged millions in oil contract losses.
As a legislator, Villavicencio was criticized by opposition politicians for obstructing an impeachment process this year against Lasso, which lead the latter to call the early elections.