the first Beloryann is found on n_d2_warehouse (the second map), around the cargo area.

after jumping from this cargo crate, youll find a few crates and barrels on your left. behind it is one of the secret Beloryann's:



here, you will find a max health powerup, and a couple grenades:



bonus fact: if you were to come back to this same spot in n_d4_warehouse02 (the fourth map), youll find that the Beloryann is gone, even if you never touched the Beloryann in the first place. youll instead find two health vials:

this one is found on s_d4_trenches02 (the fourth map).

you will find these crates and barrels covering this hole:



here, you will find a max health powerup, and a crossbow:

found on m_d1_streetground (the first map). this ones the easiest to find.

its this alleyway here, right after the alleyway you came in from. youll find it on the left after the first turn:



here, you will find a modified tommy gun with two pellets:

found on t_d4_striderplaza (the fourth map), next to the plaza.

go to this area on the left of the plaza:



go into the alleyway:



here, you will find a tommy gun: