LONDON (AP) — Britain's chief coroner has said that security failures may have played a role in the stabbing death of a policeman killed during an extremist attack on Parliament last year.

Coroner Mark Lucraft said Wednesday that "shortcomings in the security system" meant armed officers weren't guarding an entrance to Parliament when an extremist stabbed policeman Keith Palmer to death on March 22, 2017.

Palmer was one of five people killed by Khalid Massood in the attack on Westminster Bridge and Parliament.

Speaking at an inquest, Lucraft said that armed officers were not aware they were supposed to remain "in close proximity" to the gates outside the Parliament building.

He said that if they had been stationed there "they may have been able to prevent" Palmer from suffering fatal injuries.