Officers were called to Salford Royal Hospital in Greater Manchester at 9.20pm yesterday, after a man made threats towards staff, police said.
A weapon was recovered and the man was detained on suspicion of possessing a firearm and false imprisonment. A woman was also arrested on suspicion of possessing a firearm. Both remain in custody.
Greater Manchester Police said no one was injured during the incident, and inquiries were continuing.
More top news
The attack on a college in Garissa, Kenya, comes a day after President Uhuru Kenyatta declared: ''Kenya is safe".
The pre-trial hearing for a British banker, accused of murdering two women in Hong Kong last November, was adjourned for five weeks.
Conservationists say one of the UK's most threatened butterflies has recorded its best year for a decade following 2014's warm spring.