"memories may fade and witnesses dissemble, but circumstances never lie." and the circumstances of this case are forensic circumstances and they did not lie. a drive-by shooting on an alaskan highway. and a bomb sent through the mail. two apparently random acts of senseless violence, until forensic science discovered an important link. on an october night in 1990, rob chamberlain and his friend were driving along glenn highway in anchorage, alaska, headed to a local restaurant. as he approached the exit ramp, chamberlain heard a loud crack. he looked back and saw a hole in his rear window.

then he saw his friend, 20-year-old jeffrey cain, slumped in his seat and covered in blood. >> the bullet entered the back of his head, exited out the front of his head. death was instantaneous. >> cain's parents were called to the scene. >> i couldn't understand why jeff had to be the one who was shot. maybe i'm just like there is other people, why not shoot the bad people? >> jeff was a computer programmer with no known enemies. the driver, rob chamberlain, said he had no idea why they were targeted. >> our first impression was maybe it was a drug deal gone bad and somebody was following this young man and something had happened. >> we really pressed the issue, were you targeted for some apparent reason? were you involved in something? do you have any enemies? have you been involved in anything that would have led somebody to target you? >> not far from the site of the shooting, police found a shell casing on the side of the

highway. >> the bullet probably came from another vehicle that was traveling in the same direction as our victim vehicle. >> the casing was from a high-powered assault-style rifle, a heckler & koch, or hk-91. police wondered whether the shooting was intentional or a random act. >> they were concerned that somewhere there was a shooter out there, not knowing what had happened or what led to it, they just knew there was somebody out there who randomly shot a teenage boy on the road. >> it's kind of scary to think that you could be driving down the road and get shot. >> it was very tense at the time. they knew there was a shooter out there still and somebody who had just killed somebody. >> with little else to go on, police asked the public through local media outlets for any witnesses to come forward. >> i would not think it was a stray bullet. i would think somebody was aiming at that car. why that particular car, we don't know. >> but no one reported seeing anything unusual.

>> and so there wasn't a lot of traffic on the freeway incoming into anchorage at the time. so there was nobody else in another vehicle who called the police and said, wow, i just saw a guy fire a shot out of a vehicle. >> the investigation had barely started and was already stalled. >> it is an unlimited pool of suspects. at that particular time we have no idea who would have done this. we have no idea why they targeted that car. so it's just wide open at that time.

jeff cain's family and friends tried to make sense of the highway shooting that took his life. >> kids driving, speeding, maybe a car accident. but never, ever just sitting in a car and getting shot. that's something you read about in los angeles, not alaska. >> the shell casing found on the highway led police to believe that jeff had been hit with a bullet fired from another car. it looked like the shooter waited until the car exited the highway and reduced speed before firing the fatal shot. >> i believe what happened was that the suspects in this case

were pacing the victim vehicle until they could get the best shot possible. >> the next morning, news of the shooting appeared in the local newspaper. and when 19-year-old george kerr saw it, he felt he had no choice but to call police. >> can i explain my situation here? >> sure. >> these guys are -- these guys are friends, okay friends, i would say. i mean -- and i usually wouldn't rat out my friends, but this is just so severe i've got to do it. >> kerr said he and his two friends, r.d. cheely and doug gustafson, bought an assault rifle earlier in the day. later, when they were driving home, a car cut them off on the highway. >> just pissed r.d. off. so he turned to gustafson and he said shoot that mother [ bleep ]. >> he claimed gustafson raised the rifle and fired a single shot towards the car.

kerr claimed he didn't know anyone had been hurt until he read the newspaper. >> did he actually aim it like a rifle? >> it was really quick. i don't know. i was sitting in the back and i was telling him you don't want to do that. i still didn't think he would do it. >> george kerr's story of the shooting is very credible because by that time we had worked this crime scene and the highway all night. it was very consistent with what we had. and he definitely had information that hadn't been released to the media. >> kerr claimed he didn't know what gustafson did with the rifle after the shooting. investigators weren't entirely convinced that kerr would testify against his friends in open court. >> i'll be honest with you, i never trusted george, you know. he is one of these -- he's going to flip on you. he is going to flip-flop because on the one hand, he would go oh, how terrible this was, and this

kid didn't deserve to die, to the other turn talking about these are his best friends, you know. and we would die for each other. >> there wasn't any proof that all this happened other than what george was saying. see what i'm saying? so they couldn't just run in and make an arrest at that time. >> to confirm kerr's version of events, police asked him to wear a hidden microphone and meet with cheely and gustafson. the meeting took place in a restaurant at the anchorage international airport. two undercover policemen sat nearby. the recording device was in a car outside. >> george kerr said words to the effect of, you know, doug, why did you have to kill that guy? and gustafson responded with words to the effect of well, i didn't mean to, george, and absolutely corroborated what kerr had just told the detectives. >> but gustafson wouldn't say

where he hid the gun. nevertheless, police arrested r.d. cheely and doug gustafson and charged them with jeffrey cain's murder. george kerr accepted a plea bargain and agreed to testify for the prosecution in exchange for immunity. without the murder weapon, he was their entire case. >> george kerr was very important to the prosecution. without george kerr, it would have been very difficult i think to put them at the scene, and to actually have an eyewitness who witnessed not only the shooting but what happened before and after. >> but as the trial was about to begin, george kerr changed his story.

police had two men in custody for the shooting death of jeff cain based on information provided by their eyewitness, george kerr. kerr initially said that doug gustafson fired an assault rifle at jeff cain from approximately ten yards away, which killed him instantly. but soon kerr changed his story. >> it wasn't like an aim thing. it was just pointed in the general direction of the car. >> he now claimed that gustafson

pointed the gun out the window and fired a shot from 200 yards away, which hit the car. >> i believe that this was done so as to throw a bone to his friends, that is, to give them an out, to say that it wasn't first-degree murder, that maybe it was something lesser than that, like criminally negligent homicide or manslaughter. basically, something to try to appease his friends. >> the shell casing at the scene indicated the weapon was an hk-91 assault rifle. receipts from a local gun store supported george kerr's claim that doug gustafson had bought an hk-91 the day of the murder. kerr also said that he, cheely, and gustafson had been shooting the gun earlier that day, and they used a road sign as a target. investigators found that sign

with three bullet holes. to test kerr's story, investigators turned to forensic analyst robert shem. he test-fired an hk-91 into a piece of metal the same thickness as the road sign. then using a rubber-like casting substance called microsil, he made impressions of the bullet holes in the road sign and those produced by his test firing of the same type of gun. the castings were compared under a microscope. >> once i removed the rubber, i was able to establish that the holes in the sign were indeed .30 caliber, and they possessed the same rifling characteristics as an hk-91. >> the test proved kerr's claim that the boys were using an hk-91 that day. but could investigators prove the shooting was intentional?

the fatal bullet entered the car through the back window, hit the victim, and exited through the passenger side window. here, investigators got a lucky break. there was tinting film on the windows of the victim's car. >> had the vehicle not had tinting film, the tempered glass that was on the back window of the vehicle and on the passenger side vehicle would have shattered and probably been completely lost. >> the tinting film held the glass together. as a result, the bullet hole was still visible. shem took what was left of the passenger window and made a cardboard template, then recreated the bullet hole. he placed the template in the victim's passenger-side window. and then he conducted a simple test.

he ran a string from the bullet hole in the back window through the hole in the headrest to the hole in the passenger side window. >> what we found was that after stringing the trajectory, that the angle was approximately 47 degrees off the back of the vehicle. >> if the shot had been fired from 200 yards away, as george kerr now claimed, the trajectory angle would be approximately 95 degrees. but the 47-degree angle placed the shooter's car very close, within 7 to 15 yards away. >> this then put the vehicles in such a close position that it rendered a very easy shot for mr. gustafson when he shot at the victim vehicle. >> at the murder trial, george

kerr testified against his two friends but continued to insist their car was 200 yards away from the victim's car when the shot was fired. >> it's just not a first-degree murder. >> and you base that on what? >> because he was shooting out of the car, not to kill. >> but the forensic evidence proved they were less than 15 yards away, which meant the shot was intentional. based on this evidence, the driver, r.d. cheely, was convicted of second-degree murder. doug gustafson, the shooter, was convicted of first-degree murder. both were sentenced to life in prison. since george kerr had immunity from prosecution, he left alaska soon after the trial ended. but the story didn't end there.

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about a year after the highway shooting, a package was mailed to george kerr in care of his family's address in eklutna, alaska.

since george was out of state, his father decided to open it. 44-year-old david kerr was killed instantly. george's stepmother michelle was barely alive. every bone in her face was broken, her eardrums shattered. police questioned her on the way to the hospital, convinced she would not survive. >> michelle, there's some police officers here. just repeat what you think happened. go ahead. >> well, we got a package for george from the state of alaska. i know it was from doug. >> how do you know it was from doug, michelle? >> because george put him in jail.

>> okay. >> george testified. >> michelle thought the bomb had to have come from the two men her stepson put in jail, doug gustafson and r.d. cheely. >> the bomb was not meant to frighten someone, to intimidate someone. this was meant to kill. and it succeeded, killing the wrong person. >> but could the forensic evidence prove it? at david kerr's autopsy investigators found a tiny metal post in his chest, the kind used in a switch. >> ultimately, our crime lab was able to determine the type of switch that that post would be a part of, a manufacturer, and to whom did the manufacturer provide the circuit or the switch? radioshack. well, there are lots of radio

shacks, but at least we knew there were radio shacks in anchorage. >> but both cheely and gustafson were incarcerated at the time. >> how could they have done it from jail? how could they do this? how could they do that? you know, which was all of our questions. you know, how could somebody do that from jail. >> since prisons routinely record all inmate conversations, investigators found this coded conversation between gustafson and his sister peggy. it took place shortly before the bombing. >> yeah, now this is to fix your car, remember? as soon as you find out which way is on and which one is off on the sliding one, glue it in place like i described, right below the surface. >> uh-huh. >> so that when it's pushed towards the side, it's on. and when it's pushed towards the center, it's off. >> right. >> okay. >> superficially, it just sounded like doug giving his

sister some help fixing her car, but had too much connected with it to be just that. so as you listen to it over and over again, you know, it became clear that they were talking about doug was giving peggy instructions on how to create a circuit for an improvised explosive device. >> those audiotapes were the smoking gun. >> other conversations revealed peggy didn't have the technical ability to build the device, so she brought in another member of the family, their elder brother craig, who is a mechanic. apparently both peggy and craig gustafson believed their brother was innocent in the highway shooting death and that george kerr was responsible. >> to give some idea of the depth of her emotions and her feelings of revenge, peggy gustafson is nine months pregnant. she is, in fact, within three

days of delivering her second child into the world when she delivers the bomb package to the post office. >> rock phelps was in prison with doug gustafson and r.d. cheely when the bombing occurred, and he knew they wanted revenge. >> he was wanting to kill george, little george is what we called him. >> we had actually a number of inmates who told us that they had seen a list of names that raymond cheely had with him at the jail, and that cheely had told them that in fact this was a hit list. it was a list of people that he wanted to kill. and they were able to describe the list, that the first person on that list was george kerr. >> other names on the hit list included the judge and prosecutor at their trial. when peggy and craig gustafson were brought in for questioning and they heard the taped conversations from prison, they immediately confessed. >> this bombing was totally

preventable. it never should have happened. the department of corrections failed dave and failed me. their job is to protect the public and not simply house prisoners. >> michelle kerr sued the state of alaska and won more than $11 million in damages. peggy and craig gustafson both were convicted for their role in mr. kerr's murder and will serve a minimum of 22 years in jail. r.d. cheely and doug gustafson received additional life sentences. in the end, a half dozen families were destroyed and prosecutors believe there would have been more victims if forensic science hadn't ended cheely and gustafson's killing spree. >> you can't just take the science by itself and build a case, or rare occasions can you. you use a combination of what are people telling you, what do you know about this person, that

person, and you use your science. and it all just meshes right together. and it builds your case. but without that, you know, we'd still be back in the dark ages of investigating crime. flight 5935, profile of andre i can't say lube its. arab leaders, new leaders show a saudi convoy headed to yemen, plus, the funeral for singapore's founding father. hello and welcome to viewers around the united states and around the world. you are watching cnn news room.