Even before the attack, Mr. Duque, whose right-wing Democratic Center party campaigned against the peace deal with the FARC, expressed little enthusiasm for negotiating with the ELN.

Image A vigil outside the police academy. The attack on Thursday was the first car bombing in Bogotá in years. Credit... Leonardo Munoz/EPA, via Shutterstock

“If the ELN really wants peace,” he said on Friday, “they need to show the country concrete actions, like the immediate return of all kidnapped people and the end of all criminal actions.”

Mr. Botero, the defense minister, said the attacker, Mr. Rojas, had joined the ELN in the 1990s and worked as an explosives instructor. He lost a hand at one point in an explosion and thereafter was known by the nickname “Mocho,” slang in Colombia for someone who is missing a hand or arm.

In 2015, as the FARC was nearing its peace deal with the government, Mr. Rojas had tried three times to pass himself off as a member of that group to receive demobilization benefits, but FARC members rejected him repeatedly, said Mr. Botero, the defense minister.

The FARC, which has given up arms and formed a political party, worked to distance itself from the attack this week.

“We express our solidarity with the victims and their families,” the party wrote in a statement after the attack. “And we call on all sectors of the country to keep building a pact that takes violence and weapons out of doing politics.”