(a) A person commits the crime of burglary in the first degree if he or she knowingly and unlawfully enters or remains unlawfully in a dwelling with intent to commit a crime therein, and, if, in effecting entry or while in dwelling or in immediate flight therefrom, the person or another participant in the crime:
(1) Is armed with explosives; or
(2) Causes physical injury to any person who is not a participant in the crime; or
(3) In effecting entry, is armed with a deadly weapon or dangerous instrument or, while in the dwelling or immediate flight from the dwelling, uses or threatens the immediate use of a deadly weapon or dangerous instrument against another person. The use of or threatened use of a deadly weapon or dangerous instrument does not include the mere acquisition of a deadly weapon or dangerous instrument during the burglary.
(b) Burglary in the first degree is a Class A felony.