The Sepulchra Bretiera Sniper Rifle is a powerful weapon that can be gotten in Deathloop in the Updaam region during the Afternoon. Loading into Updaam to explore in the afternoon will reveal that a particularly angry enemy has left a present for you outside of Dorsey House.
To get to Dorsey House, players will need to travel all the way through the level. Head up toward the library, then keep right along the edge of the map, climbing up the different buildings as you need to. You want to make your way to Dorsey House which is the building where Aleksis throws his party during the evening in Updaam.
In the street outside the house you will see a large box with a bow wrapped around it. This, unsurprisingly, is a trap, and there are a bunch of enemies in a bakery facing the box. The building has a black shopfront and is right on the corner, near the present.
Head for the ground floor of the bakery, making sure the enemies don’t see you, and then slowly head upstairs. Open the door and they will all be facing away from you, and you can take them out quickly. On of them will drop the Sepulchra Breteira which is a very fun sniper rifle. Headshot kills against enemies with this weapon will cause their bodies to explode.