Sir Ian Blair posted a letter on Scotland Yard's Web site addressed to the metropolitan police department's personnel advising them to brace themselves for the force's most "turbulent" period in a decade due to the death of Jean Charles de Menezes, The Daily Telegraph reported Monday.
De Menezes was shot dead by officers after being mistaken for a suicide bomber as police searched for four suspects who had attempted to attack the London subway network. The inquest into his death began Monday.
Blair said police will approach the investigation "with humility" and won't use the pressure put on them to stop terrorists as an excuse for De Menezes's slaying.
"No one set out that day with any intent to let a young man die," Blair wrote. "The officers involved will be giving evidence of doing what they did with good intention. They have my support and should have yours. Nevertheless, this will be a difficult couple of months and we must brace ourselves for criticism."