>> i made a decision to walk out on my son and not get him out from underneath the truck. >> reporter: why? >> i panicked. >> at that point there is no doubt in my mind what happened here. >> reporter: detectives continued to push. as the interrogation stretched into its eighth hour, karlsen finally broke. he admitted he didn't just find levi under the truck. he saw the truck fall, and he may have even caused it to fall. >> i opened the truck door because i had to get to move the linkage for the [ bleep ] truck. when i did, it tipped and it just [ bleep ] fell over. >> reporter: and then clear pushed a little more. and that's when karl admitted he left his son to die. >> the brutal truth is you did kill him. whether, whatever your intent was -- >> i -- >> the action you took caused the truck to fall on him. >> yes, you're right. >> and the inaction of leaving him there. >> right.