Suspect Kenneth Lee Simpson barricades himself in Hermann, Missouri, home after he 'shot cop dead' a

A DRAMATIC police standoff is underway after a gunman barricaded himself inside his home following the deadly shooting of a cop.

Authorities in Missouri have issued a Blue Alert after the suspect, 35-year-old Kenneth Lee Simpson, allegedly shot two police officers.

The shooting took place at 9.19pm on Sunday night in Hermann, Missouri, 65 miles west of St Louis.

Missouri State Highway Patrol has announced that one of the two officers shot, Detective Sergeant Mason Griffith, died in hospital.

The condition of the other officer is unknown.

A source told reporters than one of the officers was shot in the head while the other was shot in the chest.

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Both were flown to a nearby hospital in a critical and unstable condition.

Simpson is barricaded in a home just across the street from where the shooting took place.

Officers are preparing to storm the home with flashbangs and a K-9, according to local news outlet KMOV.

The police were originally called to a disturbance at a branch of Casey's and got into a shootout with Simpson when they arrived at the scene.

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Simpson is reported to have a long criminal history, and has been on the run from authorities since April last year.

Anyone with information is urged to call 911.

Classes in the Gasconade County R-1 School District have been canceled for the day.

Blue Alerts are typically given to police to alert them of possible threats and help in the search for suspects who have brought harm to officers.

The U.S. Sun has reached out to the Missouri State Highway Patrol for additional information.

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