A former teacher of Minneapolis shooter Robin Westman reported concerns over her mental health years before she murdered two kids and injured 18 other churchgoers in a senseless attack.

The 23-year-old transgender shooter slaughtered eight-year-old Fletcher Merkel and 10-year-old Harper Moyski as they attended mass at the Annunciation Catholic Church, in Minneapolis, early on Wednesday morning.

When an older photograph taken before her transition appeared online after the shooting, art teacher Sarah Reely recognized her as a student who went by Bob in her classroom.

In a post to her Facebook page, she revealed that she knew Westman by the nickname 'Bob', adding: 'I knew this was a kid who needed help.'

'She was definitely odd, was really into furries and odd artwork and said some odd things, but wasn't violent towards others to my knowledge', Reely added.