He was out of his depth, one of the many individuals promoted beyond their station ostensibly because he could work as a team, which can euphemistically mean he draws the salary of a Detective Chief Inspector whilst a subordinate does the work.
He may have realized faced with mounting pressure from colleagues that he had made a mistake, but was one of those breed of men who refuse to acknowledge they have made a mistake. He compounded his error when allowing the White House Farm crime scene to be trampled on underfoot by dozens of police trainees and otherwise, reaping the whirlwind when ACC Simpson took over in October.
Notwithstanding I'm very sorry about the fatal accident. I'm sure the impending trial was preying on his mind and the evidence and justification he would be required to give.