consider (someone) armed and dangerous

To presume that someone possesses a weapon and is very likely to use it against others. Typically said of criminals, especially fugitives. Police are considering the suspect armed and dangerous. They are urging the public to use caution if he is spotted. The news reports said to consider the carjacker armed and dangerous. If he's one of the most wanted fugitives, it's a good idea to consider him armed and dangerous.