Dateline | April 10, 2013
>>> as police investigated the home invasion murder of joe morrissey , his widow kay was dealing with not only her own grief and trauma but also her son patrick 's.
>> when patrick would ask you what happened to his father, what would you tell him?
>> i tried to answer him thinking age appropriate. because he was 5 years old. and i would say, you know, daddy had a little booboo on his heart and he died.
>> reporter: kay was still trying to protect her son, just as joe had done on that terrible night.
>> even when the man was dying, that's what he was doing. he was fighting for his life and trying to protect my mom and patrick .
>> reporter: in the days after the murder police were zeroing in on randy tundidor jr . when they received an unexpected phone call . from his younger brother , shawn tundidor.
>> he tells us his brother is not involved. he actually provides his brother with an alibi. randy jr . was with me, he didn't do this.
>> you're about, what, 99% or 100% convinced that randy jr . was in fact at the morrissey house that night.
>> oh, definitely, yes.
>> so shawn 's lying to you.
>> we know shawn 's lying about that part of it, yes.
>> reporter: police knew shawn had an alibi for the night joe morrissey was killed. he was not his brother randy 's accomplice. it turned out that shawn came in not only to give his brother an alibi for the murder but to tell a story that shocked the officers. he wasted no time.
>> basically, i'm going to tell you straight up, my dad did it.
>> reporter: his father, randy sr .
>> it was a bombshell. we were surprised we were hearing the father was actually at the residence.
>> reporter: and then shawn tundidor proceeded to tell a chilling story about his father. how his dad felt wronged by his landlord, joe morrissey , and went to joe 's house to kill him. he had tried to shoot joe , but his gun wouldn't go off. so he repeatedly stabbed joe . shawn said his father was even able to recite joe 's last words.
>> he said, "i got kids. i think i'm dying."
>> reporter: according to shawn , randy sr . wore shawn 's brand new white sneakers during the murder.
>> he said trust me, they weren't white when i was done with him.
>> reporter: shawn painted a very different picture of his dad than his brother had. shawn said his dad was a violent man.
>> my father used to beat us bad. i mean, really beat us.
>> reporter: with a violent past.
>> my father is just known to be one of the craziest guys you ever met. they used to call him rampage. they used to call him scarface because he has a big-ass scar on his face.
>> reporter: and shawn said his father had been trying to scam joe morrissey out of money by breaking light switches at the rented townhouse and by faking a slip-and-fall injury so he could sue joe .
>> there was nothing wrong with that light.
>> so this fall down the stairs was a bunch of bull [ bleep ]?
>> reporter: despite all that, shawn said his brother, who he describes as having the mind of a child, looked up to their father and would do anything for him.
>> he's going to do anything and everything he has to do to make sure my father doesn't go to jail because he loves him.
>> reporter: but if his father loved randy jr . back, then why would he get him involved in the crime in the first place? and even go a step further, let his own son take the rap for it.
>> my son's already caught. [ bleep ] it. i won't go to jail, let me just throw everything on him.
>> reporter: shawn says he was more than disgusted. he loved his brother and had been protecting him since they were young. now randy jr . needed protection more than ever. which shawn felt required him to turn in his own fire for a crime of which he was not even suspected.
>> he went there to kill him.
>> reporter: shawn says the murderous scheme was set in motion when his dad received a letter from joe morrissey . it informed him that he owed just over $1,600 and his lease would now be month to month. that letter arrived the day of joe 's murder.
>> how'd your dad react to that letter?
>> like i'm not going to let him do it.
>> because it was like an insult to him?
>> he took it like that. it really wasn't. it was a man wanting his money.
>> but your dad saw it as provocation?
>> and i'm going to teach him a lesson?
>> reporter: then he says his dad roped in randy jr .
>> my brother didn't know whose house he was going to. and my brother didn't know that somebody was supposed to die in that house.
>> reporter: only to turn his back on him afterward and let randy jr . fall under suspicion for the murder.
>> he says they caught him, not me. i said, you fix this or i will.
>> that's what you said to your father?
>> i told him straight up.
>> fix this or i will?
>> reporter: and that's when shawn turned his back on his father and went to police, trying to save his brother by informing on his dad. if that didn't stun the officers, then what shawn did next did.
>> before we could even ask him to wear a wire, he offers to wear a wire. he wants his father to be held responsible for this.
>> have you ever seen anything like that before?
>> reporter: this son was going to become a police informant , wear a wire, and try to get his own father to admit to a murder. the sound quality on the wire is poor. but for police randy sr .'s guilt came through loud and clear.
>> what's the part of that conversation that says to you, guilty, we got him?
>> i think when he tells shawn that we have no case, our case is weak, he tells shawn that "she can't identify me, she can't even identify randy ." putting himself there.
>> reporter: what's more, this security video from the business next door to randy sr .'s window tint shop shows a man behind it tending a big fire a couple of hours after the murder. exactly where police had found burnt evidence from the crime.
>> you can't make out the person's identity. it's definitely a large person. randy sr .'s well over probably 300 pounds. we suspect it's him.
>> reporter: by friday night, four days after the murder, both randy sr . and jr . had been charged with a slew of crimes, including murder, attempted murder , and arson. that randy sr . would let his son take the fall was all the evidence kay 's daughter needed.
>> he's a monster. if you don't care about your own kids, you're not going to care about somebody else's life.
>> reporter: case closed? not by a