End of the prison - Gates closed

[TheVirus]

So I killed the big bug beast that wrecked all of the posts.

I went around back and noticed the gates were open so I went back there. Killed a headcrab human. Went ahead saw some fire, kept going. Gates began to close.

I ran back and .. now what?

Trying to beat the game before I review it

 

[Jonsauce]

I think you are at the trash compactor part. If you don't run back then those "gates" will close behind you. Soon the ones on the far end will close. Look to your left when you are in the middle of the chanel. You can pile up a crate or two and jump into an opening.