Law enforcement authorities remained tight-lipped about the delicate situation playing out in Midland City, a small town in the southeast corner of Alabama.
Officials from local, state and federal agencies have been camped near the bunker since Tuesday, when authorities say a gunman demanded that a student be let off a bus carrying more than 20 children home from school.
When 66-year-old driver Charles Albert Poland Jr. refused, the suspect shot him several times and fled the scene with a kindergarten student, police said.
By Thursday (local time), the gunman had been holed up for two nights with the child on his rural property.
"The negotiators are still communicating with the suspect," said Robyn Bradley Litchfield, a spokeswoman for the Alabama Department of Public Safety.
The shooting and hostage taking happened while a national debate rages over gun violence, especially in schools, after a gunman shot dead 20 students and six staff members at a Connecticut elementary school in December.
Authorities have not officially released the names of the suspected gunman or the child, who they believe is unharmed.
An Alabama legislator, Representative Steve Clouse, told reporters the boy suffered from Asperger's Syndrome and attention deficit hyperactivity disorder but had been able to receive his medication while held captive.
A school employee said the boy appeared to have been chosen at random, but police have not confirmed whether the suspect and child know each other.
Neighbors identified the man as 65-year-old Jimmy Lee Dykes and said he had been seen digging in his yard in the past couple of years and carrying a shotgun.
Ronda Wilbur, who lives across the street from Dykes, referred to him as "Mean Man" and complained he had killed her family dog by beating it with a lead pipe and then bragged about it to her husband.
Dykes had been due to appear for a bench trial on Wednesday after his arrest last month on a menacing charge involving another neighbor, court records showed.
The neighbour, James Edward Davis, told CNN the arrest stemmed from an incident on December 10 when Dykes pulled a gun on him and his young daughter. Davis said Dykes was upset because he believed Davis had driven onto his property. Dykes fired two gunshots as Davis sped off in his car, he said.
Michael Senn, a pastor, said Dykes apparently had equipped the bunker with TV and two to three weeks' worth of supplies.
"We're just encouraging everybody in this country to come together and pray for the safety, protection and the quick release of this child," Senn said.
