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
Two nursery workers in New Jersey are accused of filming youngsters fighting and posting the footage on Snapchat.
Pope Francis slipped out of the Vatican to make a surprise visit to an optician's to get a new pair of glasses.
An extra hour a day of TV, internet or computer gaming could reduce GCSE success by two grades, research claims.