(CNN)  As an armed standoff entered its fifth day Saturday, authorities negotiated through a ventilation pipe with a man accused of barricading himself and a 5-year-old hostage in an underground bunker in southeastern Alabama.

Police have been tight-lipped about a possible motive since the hostage drama began unfolding in Midland City with the shooting of school bus driver and the abduction of the 5-year-old.

In a sign of perhaps how tense negotiations are between authorities and the suspect, officials have refused to detail what, if any, demands have been made by the suspect.

On Friday, the Dale County sheriff did confirm what neighbors have been saying and news outlets around Midland City have been reporting since the standoff began -- the suspected gunman's identity.

He is Jimmy Lee Dykes, 65, a Vietnam veteran and retired truck driver who moved to the area about five years ago.

The sheriff's department released a photo of a gray-bearded, unsmiling Dykes and brief physical description: white male, 6 feet tall, weighing 170 pounds with brown eyes and gray hair.

This much is known, according to police and witness statements: On Tuesday at about 3:40 p.m., bus driver Charles Poland Jr. was shuttling children from school to their homes when he dropped children off and the gunman boarded the bus.

The gunman demanded that Poland, 66, hand over two children. Poland refused, blocking access to the bus's narrow aisle as at least 21 children escaped out of the back emergency door, according to police.

The gunman shot Poland four times, killing him; grabbed the boy and then barricaded the two of them inside a nearby bunker.

It's unclear whether the gunman was after a specific child on the bus. Police have said there is no connection between the suspect and the abducted boy, whose identity is being withheld.

The suspect, who police have identified as Dykes, is holed up in a bunker 4 feet underground and built at least partially out of PVC pipe, authorities have said.

A hostage negotiator has been communicating with the alleged gunman through a 60-foot-long plastic ventilation pipe in an effort to end the standoff.

Authorities believe the boy is physically unharmed.

The suspect agreed to let police send down coloring books, crayons and prescription medication that the boy needs for treatment for Asperger's syndrome and attention deficit disorder, State Rep. Steve Clouse told CNN.

Neighbors have said the bunker has electricity, and Dykes has been known to stay in it for up to eight days, said James Arrington, the police chief in nearby Pinckard.

Dykes has been described as a self-styled survivalist with "anti-government" views, according to the Southern Poverty Law Center's Hatewatch.

As negotiations continue, preparations were under way for Poland's funeral.

The late school bus driver will be memorialized Saturday night at a visitation service, followed by a funeral service Sunday at the Ozark Civic Center.

Alabama Gov. Robert Bentley praised Poland for protecting the children on his bus.

"He stood in that place, and when that man came to take two children, he said no. And he lost his life because of that ... he did his job, and I'm proud of him as the governor but I'm just proud of him as a human being," he said.Authorities Tight-Lipped As Standoff Over Child Hostage Enters 5th Day