Three Leicestershire Police officers are under investigation over how they dealt with alleged assaults by Valdo Calocane the month before he killed three people in Nottingham.
Watchdog the Independent Office for Police Conduct said two constables and a sergeant have been told they are being investigated over how inquiries were progressed.
It is claimed that Calocane assaulted two colleagues at an industrial estate in Kegworth, Leicester, in May last year.
The following month, he went on to kill students Barnaby Webber and Grace O’Malley-Kumar, along with caretaker Ian Coates, in a knife rampage in Nottingham.
