but it s not answering what s wrong with this kid, cause he s incredibly sweet. how does he walk into a room with a shotgun, this kid? and it doesn t add up. i mean, i m totally, totally puzzled. and that s when i bring in vicary. reporter: dr. william vicary, then a forensic psychiatrist and a graduate of harvard law school, agreed to meet with the brothers in jail. he knew going in, police believed lyle and erik killed their parents for money. but based upon the dozens of parricide cases that i had worked on in the past, that s the exception. that s not the rule. the rule is that something horrible is going on in the family. reporter: and something was going on in the menendez family. something very secret. but what was it? reporter: coming up, new evidence seen on television for the first time. a letter from lyle to erik, hinting at the horrors in that house.
Police uncovered seven bodies buried in the backyard of Dorothea Puente s Sacramento home in 1988
Officers did not initially suspect the seemingly-sweet grandmother had anything to do with the crime and let her take off for a coffee
Puente fled, prompting a four-day nationwide manhunt that ended in her capture
She was put on trial for the deaths of nine people, seven of whom were tenants who had leased bedrooms in her home
Puente was convicted of three murders and sentenced to life in prison; she died in 2011 having refused to confess to her crimes
A new documentary airing on Oxygen, titled Murders At The Boarding House, explores the infamous case