New documents show multiple people knew the killer was abusive towards his wife and one said he spoke often of disposing bodies.
A former neighbour, a Canadian Forces veteran, says she told police about the gunman’s weapons and domestic violence and nothing was done.
RCMP say they also found out where the gunman hid overnight before he started his second wave of killings.
Canada is trying to piece together exactly what happened during the country's deadliest modern-day shooting that killed at least 22 people in Nova Scotia over the weekend.
Several of the victims are believed to be unaware there was an active shooting situation happening.
Two young people died and 15 people were shot when lone gunman Faisal Hussain opened fire in the Danforth late Sunday night. Hussain died at the scene.
Several established conspiracy subcultures jumped at an opportunity to push media-discrediting agendas.
Alek Minassian has been charged with 10 murders. Before the attack began he allegedly posted his support for Incel and praised mass murderer Elliot Rodger.
Minassian, 25, has been described as intensely socially awkward and has been connected to an incredibly misogynistic online group.
Facebook has confirmed to VICE that the post linking Alek Minassian, accused of killing 10 people, to the misogynistic group is real.
"The nature of the alleged crime and the resulting harm compelled this decision," said Attorney General Loretta Lynch.
Holmes killed 12 people and injured 70 in a 2012 shooting spree. Now he could face the death penalty.