Transcript for The day the 1993 Waco siege came to a horrific end
This is ABC news "Nightline." What began as a fiasco on the 28th of February ended as a total disaster today. Reporter: 25 years ago this April, the standoff outside Waco, Texas, between a controversial religious group and federal law enforcement came to a horrific end. It was our earnest hope that we could try to negotiate without any -- without endangering human life. Reporter: For 51 days, the protracted confrontation captured the nation's attention, becoming T longest-running siege in American history. Ending in the deaths of more than 70 men, women and children. For some Americans, this was a legitimate law enforcement operation against a cult that was stockpiling weapons. For others it was an overreaching and violent federal government. Reporter: The man at the center of it all, charismatic sect leader David Koresh. The man is David Koresh. David Koresh. David Koresh. That's what David wanted, was everyone to pay attention to him finally. And he was getting what he wanted. All eyes were on him. He was highly unstable, self-proclaimed messiah who used the bible and used scriptures as a weapon. Reporter: The 33-year-old was the leader of the branch davidians, offshoot of the seventh day adventist church. We knew it was a cult, we'd joke about it all the time, yep, we're cult members. God can't manifest his love in this world of darkness! You got to come up there to find out about god! Reporter: In the 1980s, Koresh and over 100 followers lived together on a compound called mt. Caramel center ranch. It was important for David Koresh to isolate the group from the world, because the world is an influence that is constantly pulling people away and distracting you from the message. Koresh called his compound the ranch apocalypse. The men lived on the ground floor, the women on the second floor with David Koresh's bedroom up there too. There was a gymnasium, there was a chapel, a large kitchen, and there was a shelter. A buried school bus where they could go to in an emergency. There was no running water, no heat, no electricity of any kind. We had to go to bible study three times a day. Reporter: Koresh practiced polygamy, taking multiple women as wives and fathering their children. There was an extremely strong sense of family within that group. And they were that family. And anybody else was not. Anybody else by their definition, by their verbiage, was babylon, evil. Reporter: The group had stockpiled weapons they say for self-defense. David Koresh preached from the beginning he wanted to militarize his followers. He started going to gun shows and purchasing huge amounts of weaponry, ammunition. He thought that the end of all-time, the end of the world, would come in a great battle between the faithful and the beast of babylon, who he specifically identified as the government of the United States of America. It's war! These governments of this world are coming to an end. Go ahead and laugh. He had been saying for such a long time they were going to come for us. And then they did. They came. And they did exactly what he said they were going to do. One of the reasons that the branch davidians started to get investigated by the ATF was because one day a delivery man for U.P.S. Delivered a box of grenades to David Koresh, and the box broke open. Reporter: The investigation involved suspicion of firearms offenses, as well as potential physical and sexual abuse of minor children. The FBI underestimated the charismatic control David Koresh had over this faith community. David Koresh was training soldiers for god. Religious zealots. Reporter: February 28th, federal law enforcement moved in to raid the compound. You could hear something rumbling. Coming right at us. They were never able to determine who really shot that first shot. Reporter: Someone inside the compound called 911. 911, what's your emergency? 75 men around our building and they're shooting at us in mt. Caramel. Tell them there's children and women in here and to call it off. Wayne, cease firing. I have a right to defend myself! We did lose the call. Call back, got hold of Koresh. What'd you guys do that for? You see, you brought your bunch of guys out here and you killed some of my children. We told you we wanted to talk. No, how come you guys had to be ATF agents? How come you try to be so big all the time? Reporter: After a few hours the shooting stopped. Four federal agents and six branch davidians were dead. But the raid had failed to flush the davidians from their compound. My feelings were, this is not over. When a cop goes down, it's a free-for-all. They want revenge. We wanted pay back, let's go regroup, let's go finish this thing. Reporter: The standoff lasted for days, then weeks. The situation began to grow desperate on both sides. The main focus was on the children. David agreed to send them out two by two if we would read a specific scripture that he gave over the radio. My name is Dave Koresh. I'm speaking to you from mt. Caramel center. We got six children out the first day. He says he will release more children, two by two -- A total of ten children released from the compound -- He wanted the public T think that if they died, they died at the hands of law enforcement. But still there has been no surrender. We made a request that they prepare a videotape of the folks inside so that we could put a face to a name and get a sense of their personalities. This is my family. May not be like your family. We were stunned when we saw all those precious little kids that were his biological children. Her name is serenity. One of the things that was very, very clear is that these kids were afraid of David. Love me? Have a kiss? Thank you. The standoff near Waco is in its fourth day with no end in fight. The FBI says 90 adults and 20 children remain in the compound. Give me the coverage. I'm going to get your scripture message to the radio station right away. We came up with the idea of saying, if you'll record a message and in that message you promise to peacefully surrender. He did that, we were very hopeful. We were all prepared to receive them. And bring them out. All of a sudden, everything went quiet. Koresh reneged on it, changed his mind. My god told me to wait, and it's all I'm doing. We're dumbfounded. It escalated things to a point where, in response, the FBI advanced onto the property with its tanks. You want to go knuckles to knuckles now, you want to have an all-out? Reporte The 40th day of the siege at David Koresh's compound is ending like the other 39. 51 days had passed, we hadn't had a person out in over a month, we haven't had a child out since the 5th of March. Enough's enough. Reporter: April 19th, law enforcement decided to move in with force. When I looked through the binoculars, I saw a tank with an extended arm, then we realized they were going in. David, it is time to submit and surrender to the proper authorities. Over the loud speakers, we began to put gas into the building. This gas will temporarily render the building uninhabitable. The strategy is to make things so uncomfortable for Koresh and his followers that they will come out with their hands up. And then it seemed sudden. The place is on fire! The place was engulfed in flames. I'm persuaded by the recordings of what was being said inside mt. Caramel that David Koresh and his most loyal followers decided to set the fire. You want to pour it already? We want the fuel! You want some here? Pour it all out. We might need some later. My thought was, I'd rather be shot than to burn. Two FBI guys, he was telling us to get down, the siege is over. I looked up to him, I said, the kids should be in the underground bus. He looked at the other FBI guy and the other FBI guy said, we tear gassed that bus. I was thinking to myself, you tools. You tear gassed the only avenue of escape for the kids. 78 people would perish that last day. Not a one of them had to. We were not successful getting those children out. And boy, that was -- a traumatic thing. Reporter: The standoff had finally ended, but the legacy of the siege would be lasting. Timothy Mcveigh was there. And was so affected by the incident at Waco that he became an anarchist. Federal building in Oklahoma City was rocked this morning by what some are speculating was a car bomb. The attack may have been revenge for the federal raid in Waco, Texas. Reporter: There are branch davidians still worshipping in America. Today at the site of the former compound, a memorial to the dead. The memorial in Waco, I have been to several times. Just brings back the senseless, useless feeling that this didn't have to happen. Ultimately, I would say we never had control over how it was going to end. That was David. He made that decision.
This transcript has been automatically generated and may not be 100% accurate.