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
It was a cloudy start across many eastern areas first thing. However, Sunday shaping up to be a warm sunny day for most.
Former Work and Pensions Secretary Iain Duncan Smith has David Cameron should remain prime minister even if Britain votes to leave the EU.
Tony Blair has said Leave campaigners are focusing on immigration "because they've lost comprehensively the debate on the economy".