The Texas UPS driver who unwittingly delivered guns and ammunition to notorious cult leader David Koresh in the lead up to the deadly Waco siege two decades ago has spoken for the first time about his accidental role.

Larry Gilbreath had regular contact with Koresh and his followers in the lead up to the siege in April 1993 given he was the one to deliver packages to the Branch Davidian Church compound in Waco.

Gilbreath broke his silence in an interview with 48 Hours, set to air on CBS on Friday, as the 25th anniversary of the infamous 51-day standoff nears.

Koresh was among the 76 people, including 18 children, that died when an armed stand-off between FBI agents and the religious cult came to an end at the compound on April 19, 1993.

Larry Gilbreath, the UPS driver who delivered guns and ammunition to cult leader David Koresh in the lead up to the deadly Waco, Texas siege in April 1993 has spoken for the first time

Gilbreath, who is now retired, said he is still haunted by the violent ordeal and that many have blamed him for what happened.

'I've kept my story secret for the last 25 years. I didn't want to take this to my grave,' Gilbreath said. '

'We paid a pretty good price. I have been blamed for what happened out there.'

Gilbreath said he had noticed the packages he was taking to Koresh had been getting bigger and heavier over time about a year prior to the siege but was oblivious to what was being planned.

'I thought it was a little strange that religious people would be ordering guns,' Gilbreath said.

'I'd say probably 75 percent of the time, when I would get there, David always came out. He signed for a lot of 'em.'.

It wasn't until February 1992 when a box of hand grenades accidentally opened prior to delivery that he first alerted authorities.

Notorious cult leader David Koresh was among the 76 people, including 18 children, that died when an armed stand-off between FBI agents and the religious cult came to an end in 1993

Gilbreath later learned he had been delivering ammunition, 223s, AK-47s, ART-15s and even a grenade launcher to the cult compound as Koresh planned the battle with authorities

A 51-day standoff with Koresh came to an end when FBI agents stormed the compound. In the ensuing chaos and gunfire, the church buildings caught on fire and 76 people ended up dead

He said his wife Deborah called the sheriff who then alerted the ATF.

It was when authorities got involved that he learned he had been delivering ammunition, 223s, AK-47s, AR-15s and even a grenade launcher to the cult compound as Koresh planned the battle with authorities.

Gilbreath started working with the ATF undercover until one day when he believes Koresh cottoned on to the operation.

'Outta nowhere, David just looks at me, and says, 'Larry, I know they're watching us,'' Gilbreath said.

'I went numb.'

What happened from there ended up becoming one of the deadliest confrontations between law enforcement and civilians in US history.

In a botched ATF raid on February 28, 1993, four agents and six Branch Davidians followers died as authorities tried to arrest Koresh for supposedly violating federal firearms laws. The cult leader was seriously injured.

The FBI raided the compound on April 1993 and ended up in a shootout with Koresh and his cult followers

Ex-follower Grace Adams said Koresh would abuse girls as young as 12 years of age, while Joann Vaega said she could recall Koresh planning for the siege

The events at the Branch Davidian compound ended up becoming one of the deadliest confrontations between law enforcement and civilians in US history

The FBI then took over and began a standoff as Koresh and his followers barricaded themselves in the compound. It ended when attorney general Janet Reno gave the go-ahead to attack the building and remove the members by force.

In the ensuing chaos and gunfire, the church buildings caught on fire and 76 people ended up dead.

Koresh, who claimed he was the son of God, had built up a following at the Branch Davidian Church, where he had 13 wives and fathered 19 children.

The Branch Davidians, a splinter of Seventh-Day Adventists, believe Christ's return to earth is imminent and that the scriptures give clues on when that Second Coming will be. Modern day prophets enlighten their members and preparing them for that day.

Details about the bizarre activities at the Branch Davidian camp have emerged in the last two decades in various memoirs and accounts from former cult members.

He preached for 15 hours a day and believed that he had total control over all women on Earth.

The most sinister part was the alleged abuse of underage girls.

Koresh claimed he'd been ordered by God to have as many wives and sex with whom he pleased. It's thought he had at least 13 wives and fathered 19 children at Waco

In an interview with 48 hours, former follower Grace Adams said Koresh would abuse girls as young as 12 years of age.

'As a woman, you needed to have sex with David in order to go to heaven,' she said.

Adams said she fled the compound after Koresh locked her in a 10-foot by 8-foot room for four months.

Another ex-follower Joann Vaega, who was a toddler when her parents moved to the compound in 1987, said she could recall Koresh planning for the siege.

'My mom made the bulletproof vests... We were getting ready for war,' she said.

Vaega said she was one of the children allowed to leave after the initial botched raid. Both her parents died in the final confrontation at the compound.

Secrets of Waco will air on Friday, December 29 at 8pm on CBS.