Shirley recalled that Davis had these mysterious instakilling talismans that killed Emperor Tritor and Emperor Raven back in the day. So she felt that it was either Davis or someone else who killed Top Disciple Lauren Zucker.
However, till secretly killing and somehow making it look like a suicide, she understood as she more or less knew that his killing talismans had killed their souls since there weren't any injuries on Emperor Tritor and Emperor Raven last time, but how Davis or some other people had him write a suicide note, and that too something pointed at Grand Elder Valerian who had the most distinguished position in the Elder Hall was something she couldn't understand.