Canadian police had yet to determine a motive for the country's worst mass shooting, as the death toll from the carnage in Nova Scotia over the weekend climbed to 23 from 19, the Royal Canadian Mounted Police (RCMP) said on Tuesday.

The shooting rampage has rattled rural communities in the Atlantic province, as investigators seek answers to questions such as how the gunman obtained an authentic police uniform and secured a police look-alike cruiser, both of which aided his easy movement during his 13-hour spree.