Velasco was a high ranked member of the Medellín Cartel.
He's first seen with Pablo Escobar as one of his men working in La Catedral. He's one of his most trusted men and the one who commands the rest. He manages to escape the Colombian Army assault.
Later, he's almost always very close to Pablo, passing him all the information about the situation in Medellin.
He's finally captured thanks to the information given by Maritza to Peña. His captors are the Pepes, a combined force of the paramilitary and members of the Medellin Cartel loyal to Judy Moncada. He's interrogated and tortured by Don Berna, who gets some information from Velasco. His dead body is found in Medellin a few days later, with a open letter signed by Los Pepes.