Quinonez, 32, and another person were found dead close to midnight local time (0500 GMT) on Friday, according to police.
In response, Ecuador’s President Guillermo Lasso on Saturday decreed a state of emergency throughout the country. Set to begin Monday, the order will last 60 days with the military to take to the streets to patrol and carry out searches.
“Those who take the lives of Ecuadoreans will not remain unpunished. We will act with force,” Lasso tweeted.
The provincial governor likewise pledged accountability for the murders.
“No one will rest until @PoliciaEcuador captures the culprits. We are facing a war against drug gangs that intend to subdue us,” Pablo Arosemena, the governor of the Guayas province, whose capital is Guayaquil, said on Twitter.
The country’s Sports Ministry first confirmed Quinonez’s killing on Twitter, paying tribute to “the greatest sprinter this country produced.”
“We have lost a great sportsman, someone who allowed us to dream, who moved us,” the ministry said.
Quinonez held Ecuador’s record for the 200-meter sprint with a time of 19.87 seconds.
He was a finalist in the 2012 London Olympics, achieving seventh place after competing in the semis in the lane next to Usain Bolt, the fastest sprinter in history.
Ecuador’s Olympic Committee said the death of Quinonez “leaves us with profound pain” and that his “legacy will forever stay in our hearts”.
The sprinter’s body was due to return to his hometown of Esmeraldas on Saturday night.
A tribute Sunday will see the athlete’s coffin placed in a burning chapel in a football stadium in the town, said the Ministry of Sports.
Quinonez’s killing comes as violence has spiked dramatically in Ecuador in recent months: between January and October this year, the country registered almost 1,900 homicides, compared to about 1,400 in all of 2020, according to the government.
The athlete was preparing for training in the United States with a view to his official return to the tracks and eventual participation in the World Athletics Championships in Oregon next year.
The Ecuadorian Olympic Committee (COE) said that “the surprise departure” of Quinonez “leaves deep pain, but his legacy as the greatest sprinter in our history will always remain in our hearts.”
“Regrettable about our dear #alexquinonez, my heartfelt condolences to his family and his loved ones,” fellow Equadorian athlete cyclist Richard Carapaz, who won gold in the men’s individual road race at Tokyo 2020, said on Twitter.
A serious contender for the podium at the Tokyo Olympics, he could not compete due to a sanction from the International Athletics Federation for not correctly reporting his whereabouts for out-of-competition anti-doping tests.