tonight -- >> we have a report of gunshots. >> inside the investigations. >> someone has to be held accountable. the truth has to be found. >> how could an al qaeda member make it onto a u.s. military base? >> america has been betrayed. >> survivors and families of the pensacola terror attack demanding change. >> he is a hero. he did his duty. he was at his post. >> what it all reveals about the flaws in our own system. >> he fooled you. >> you could say that. >> this special edition of "nightline," "the enemy inside," will be right back. find your breaking point. then break it. every emergen-c gives you a potent blend of nutrients so you can emerge your best

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this special edition of "nightline," "the enemy inside," continues. here now, david scott. >> dear mom, i want you to know how much you mean to me. >> i miss him like crazy. my heart hurts every day. >> reporter: benjamin and sheila watson are haunted by memories of their son, caleb. >> there's no doubt in my mind

that caleb would do his duty. he was a person that was willing to serve. a person that was willing to put his life on the line. >> i still want to be just like you, dad, a hero. love, your best friend and son, caleb. >> sheriff's office, 911. >> pensacola, gunshots in building 633. >> i said, if anybody can handle this, it's caleb. >> all units, active shooter at nas. >> we got an officer down. >> i heard the first shot. i heard people screaming. >> praying. god help me. then i get shot. >> reporter: a terror attack on american soil. >> saw him. i looked him dead in the eye. >> reporter: a military officer from a foreign ally pulling the trigger on a u.s. military base.

>> america has been betrayed. >> someone needs to be held accountable.p>> reporter: saudi al qaeda terrorist. >> he's wearing a flight suit. >> reporter: two years later, what the investigations reveal about a key u.s. ally and the flaws in our own system. >> he's inside the wire, basically, as you would say in the military. >> reporter: that could leave america vulnerable to attacks from an enemy within. >> he fooled you. >> you could say that. >> your dad was so, so proud. caleb was born into that post-9/11 world. we always knew that he was going to be a soldier. >> reporter: ensign joshua caleb watson was born the third of three boys, and while he may have been small in stature, his determination could move mountains. >> if they said you're too little, he worked harder. >> reporter: while at the u.s.

naval academy, caleb was captain of the rifle team and an expert marksman. >> he said, you know what makes the united states of america a superpower? i can remember it just like it was yesterday. he look the me right in the eye and said, the united states navy. >> reporter: after graduating, he wanted to be a pilot, a path that would bring him to pensacola, just two hours from home. not only are all navy and marine pilots trained there, so are foreign pilots on exchange programs from countries all over the world. >> he's like, dad, everybody i've met, every one of them are just like me. they want to serve their country. >> reporter: what happened on december 6th, 2019, would be something the country had not seen since 9/11. an attack by a foreign national on american soil. that morning, caleb was finishing the overnight watch shift at building 633.

>> he was the officer on deck. he was in charge of making sure the building was safe. >> reporter: airman george johnson, a young father who had been in the navy less than a year, was just coming to start his day. >> i imagine for somebody devoted to may have avionics, pensacola is kind of shangri-la, right? >> the sound of freedom, best way i can explain it. blue angels practicing every other day. it was amazing. >> reporter: also there, jessica pickett, a married mother of four, and 20-year navy veteran who worked as an administrative clerk. >> did it ever once cross your mind that that base could be the target of a terror attack? >> a threat in pensacola? like, this is where people vacation. >> 7:00 starts rolling around.

officer alshamrani walks past. >> reporter: 22-year-old mohammad alshamrani, second lieutenant in the saudi air force, part of a pilot training program. >> i tried to say hello, good morning. he looks into the office, passes me, doesn't say a word, but a smirk. he continues to walk on. and as i'm waiting, i hear what sounds like a binder fall and hit the ground. like a loud clap. then shouting. "no, stop, stop." screaming. >> reporter: the first shots were fired at the watch station just off the main entrance where caleb watson and private first class cameron walters were posted. it was the 21-year-old's very first day on watch duty. both men were unarmed. cameron died immediately. caleb was badly wounded and left for dead. >> i went into my supervisor's

office, i hid under his desk. >> i was praying, "god help me." then i hear the glass break. and then i get shot. he fired. stopped. reloaded. kept firing. i thought i was going to lose my life. it was as if, you don't move, you die. >> reporter: johnson and two co-workers jumped out the window to escape. he had been shot seven times. ask he could still hear the gun firing. >> all units, active shooter at nas, building 633 on the main side, units responding, channel 3. >> reporter: at the watch station, caleb watson, badly wounded, dragged himself to the lobby, yelling at incoming sailors to leave, take cover. but alshamrani returned and shot him again. another unarmed american airman, 19-year-old mohammad hypen, fresh out of boot camp, heroically ran into the building

to help. alshamrani killed him with a shot to the chest. >> i saw his boots and his uniform. >> reporter: by the time he got to her, jessica says the killer never said a word. >> all i could think was, how could somebody in uniform do this? he ended up hitting me nine times. i had a home i had to take care of. i tagged them all and told them i loved them. >> 911. >> there's a large number of police officers that are entering the area right now. >> we've got all our deputies headed that way to respond. >> reporter: caleb watson managed to wake his way outside, severely wounded and bleeding out. he still provided law enforcement with an accurate description of the gunman, who they were about to confront. [ shot ]

>> hit, hit! >> [ bleep ]. >> hit, hit! [ shot ] >> he's wearing a white suit. >> active shooter now. >> we're confirming all shooters are accounted for. >> as long as there's only one, he's down. >> reporter: as the eight people shot and wounded were raced to local hospitals, sheila and benjamin watson were just finding out something was wrong in florida. >> i had a sinking feeling in my stomach. all his hopes and dreams. were crushed in an instant of hatred. >> reporter: within hours they discover hot caleb's killer was, alshamrani, a saudi airman, a supposed ally. >> we knew that caleb might make the ultimate sacrifice. but in florida? on our own soil? someone who came here with a

purpose, to punish americans. >> reporter: cameron walters and mohammad hithem's families would also get that devastating news. >> when i saw them at the door, i just knew. they didn't have to say a thing, i knew. >> i was curious. furious. this should never happen. can't happen. this thing is so full of failures. both in saudi arabia and the united states of america. >> king solomon of saudi arabia just called to express his sincere condolences and give his sympathies to the families and friends of the warriors who were killed and wounded. >> reporter: within the first day, disturbing details came to light, especially when al qaeda claimed responsibility, saying alshamrani was one of their operatives and had been for years. leading to major questions about how the saudi and u.s. governments could miss that.

pleoperation.a has my view would be, trust but verify, and don't just take lip service and think that that's enough. >> reporter: president trump assured the american people the saudis said they would help the families and survivors. did that happen? >> i haven't even gotten "i'm sorry." >> where is their promise? what a lie. coming up, the new fight pitting the survivors and families of the fallen against one of the richest nations in the world. and demanding answers from the pentagon. people everywhere living with type 2 diabetes people everywhere living with type 2 diabetes are waking up to what's possible with rybelsus®. with rybelsus®. with rybelsus®. ♪ you are my sunshine ♪ ♪ you are my sunshine ♪ ♪ my only sunshine... ♪ rybelsus® is a pill that lowers rybelsus® is a pill that lowers rybelsus® is a pill that lowers blood sugar in three ways. increases insulin when you need it... increases insulin when need it...ases li decreases sugar... when you need it... decreases sugar... decreases sugar... and slows food. the majority of pelsus®sur d

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continues. here again, david scott. ♪ ♪ >> his uniform. bullet holes in it. >> reporter: for sheila watson, every memory of her son caleb is precious, even if it's painful. >> this is where he was shot in the back. sometimes the imagination's worse than reality. i had to see. i had to touch. it also keeps me pushing. >> reporter: in the two years since caleb was killed in the terror attack on the pensacola base, the navy has renovated building 633. >> turning to the building, returning to the building is probably one of the hardest things that i've done. >> reporter: inside, memorials to honor the fallen. and new added layers of security. this entryway was once open.

now a wall of bullet-proof glass which extends to the watch station window. there are also additional watch positions down the halls. >> oh, we have bullet-proof glass now. that's great to keep the bullets in. because you've done nothing to keep them out. >> reporter: the shooter, mohammad alshamrani, had been in the u.s. for more than two years, one of thousands of saudi pilots who have taken part in a training program sponsored by the pentagon. >> what happened here was a terrorist attack. >> reporter: gary reid is the director for defense intelligence. >> he's inside the wire, basically, as you would say in the military in a trusted status. and that trust is betrayed. >> he fooled you? >> you could say that. >> reporter: yet in the months after the terror attack, government reports laid out a stunning profile of a man with longstanding terror ties who still somehow made it through vetting by both saudi arabia and the u.s. >> the evidence shows that the shooter was motivated by jihadist ideology.

>> reporter: the department of justice revealed what the fbi found during its investigation, that alshamrani had significant ties to al qaeda and the arabian peninsula dating back to 2015, years before he entered the u.s. the doj also acknowledged that alshamrani had written anti-american and anti-israel posts on social media. did none of that come to light in your own vetting? >> there was no indications of his involvement in any terrorist activity. >> most american children could know how to scrub someone's social media. how is it possible that no one in the military did? >> again, i can't rewind the clock and say what could have happened if someone would have done something differently. it's a complicated process, and sometimes inconclusive. there's not a perfect tool for doing that. >> reporter: the pensacola families are now suing saudi arabia, saying its own willful or grossly negligent acts resulted in sending a trojan

horse terrorist into the u.s., claiming authorities should have known he'd been radicalized since his anti-american statements weren't secret. the kingdom of saudi arabia also says they had no idea alshamrani was a problem. the parents find that very hard to accept. do you find it hard to accept? >> i'm not in a position to say what saudi arabian government knows or doesn't know about anything. >> reporter: since alshamrani's rampage, the u.s. government has updated its protocols to include insider threat programs and what it calls continuous vetting, which includes a closer, ongoing look at things like social media. >> this is a very strategic program, and we rely on foreign partnerships to protect this country. >> the parents and survivors think that the saudis are given too much deference because they're considered an important diplomatic and military ally. >> what i can tell you is this process is applied to all of the

partners equally. and i'm not aware of any special exceptions for any country. >> saudi arabian government, they buy billions of dollars' worth of military hardware. that's a huge economic impact. >> reporter: retired fbi agent ken williams has long studied islamic terrorism, investigating al qaeda back before 9/11. >> i don't trust saudi arabia. if they do not help us in resolving the issues with respect to the events of 9/11, and with the events that took place on december 6th, 2019, with alshamrani, then they are supporting evil. they are in bed with the devil. >> reporter: bill yamwilliams i expert in a lawsuit brought by the 9/11 families trying to prove the saudi government was complicit. the pensacola families' lawsuit aims to do the same thing. back in september, the saudi embassy called any allegation of complicity in the 9/11 attacks malicious and categorically false, and previously said the pensacola shooter did not

represent the saudi people. >> i don't think there has been any type of blowback against the saudi arabians. i find it quite repulsive, and it's really disheartening. 2018, you know, we have a journalist, a saudi dissident, "washington post" journalist, jamal khashoggi. we point out we know they did it. they're not held accountable. >> reporter: so far the kingdom has not commented on the pensacola lawsuit. >> i'd just like to ask you a quick question -- >> reporter: neither saudi arabia nor its lawyer responded to our request for a comment on this story either. despite what these families and survivors have been through, a deep and abiding love of the navy endures. last month, jessica's oldest daughter, desiree, left for boot camp. >> i hope she is strong enough to make the navy a better place. >> reporter: the navy has honored the survivors and the fallen for their courage on that dark day two years ago. caleb watson and george johnson were among those awarded the

purple heart. >> it's one of those things that you want it if you don't have it. once you have it, you don't want it or wish you never had it. >> reporter: sheila and benjamin watson feel the same way. they visit caleb's empty house. unable to give up this place that transports them back to a time when he was alive. >> sometimes i just stand right here, just hold on to him. i smell him. i feel him. it's all i have left. >> i know that he is a hero. that he did his duty. he was at his post. but i wish i'd never heard that word. i wish i could just talk to my boy. >> my heart hurts every day.

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♪ finally 3 says there's a time for all seasons. for the families in our investigation tonight in time may you find peace and answers. that's "nightline" for this evening. catch full episodes on hulu. see you back here same time tomorrow. thanks for the company, america. good night.