PCs Fiona Bone, 32, and her colleague Nicola Hughes, 23, were unarmed when they were killed on the Hattersley Estate in Greater Manchester.
The pair were responding to reports of a burglary and died in a gun and grenade attack from a single assailant.
Sir Hugh said that policing was sometimes unpredictable and that officers faced risks.
He said: "Sadly it's part of policing. It shows just how extraordinary the job is we ask our frontline officers to do and nine million calls a year are responded to in that way.
He said: "Policing is a risky business.
"As we speak officers will be responding to calls not knowing what they'll get to and not knowing exactly what they'll be dealing with when they arrive, and tragically, on occasion, things go horribly wrong.
He added: "Nicola and Fiona were doing exactly what their community and their chief officer wanted them to do."