Unless it's on the schedule they always lock the doors. Churches tend to have valuable items in them that can be stolen and sold for lots of money. Another reason is they could've just not had enough staff, and the Lord will understand if you can't pray in the church, he'll still hear you if you're at home. Also one of the priests also announced 6:30 Monday mass was going to be in a different building.
Doors to the chapel normally open at 7am
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