Based on the new evidence:

Gwin's viking hat was valuable. A random penguin "thought" that he was Rsnail, and sent a buddy request. After Gwin accepted, the stranger asked for a signature. Gwin was signing his autograph when the stranger slowly retrieved Gwin's hat off his head. Later on, the stranger took Gwin's puffle, too, and put him in a tree with Gwin's hat, South-East from the Mine Shack. He then made a split in a pillar on the Mine Shack roof. Gwin realized later that he had lost his hat, so he searched. He spotted a puffle in a tree wearing a hat. He wanted a closer look, so he climbed onto the Mine Shack, seconds later, the pillar cracked in half, and Gwin fell into the snow.

Evidence:

1. Finger prints belonging to Rsnail were found on the pillars, puffle, and hat.
2. Someone knew that Gwin was impersonating Rsnail, and must've told him.
3. Gwin's puffle was found, after a fall in the forest, South-East of the Mine Shack.

Damen can you meet me at the mine?

I have a second answer to what could of happened to him...
i think his friend went on top of the mine shack with him and pushed him making him fall but when he fell he didnt die because the snow was soft and then when Gwin tried to get up his friend ran over and started pushing his head down in the snow sufforcating him so that could of been a reason why he was laying faced down in the snow and then once he died he took the wood and put it all over the place to make it look like he fell and then he ran off with the hat.

Is my idea close? Its on page 3. Thanks -Archie

I have a second answer...
i think his friend went on top of the mine shack with him and pushed him making him fall but when he fell he didnt die because the snow was soft and then when Gwin tried to get up his friend ran over and started pushing his head down in the snow sufforcating him so that could of been a reason why he was laying faced down in the snow and then once he died he took the wood and put it all over the place to make it look like he fell and then he ran off with the hat.

Maybe he fell because he was trying to fix something and he might have fell and died.

I have a second answer...
I think his friend went on top of the mine shack with him and pushed him making him fall but when he fell he didn't die because the snow was soft and then when Gwin tried to get up his friend ran over and start pushing his head down in the snow sufforcating him so that could of been a reason why he was laying faced down in the snow and then once he died, His friend took the wood and put it all over the place to make it look like he fell and then he ran off with the hat.

or maybe his friend was helping him make something and Gwin might have fell and died because his friend pushed him by accidently.

Hello, Detective Bob Here. This Is What I Think: When The Penguin Asked Gwin For His Autograph And Friend Request, Gwin And The Penguin Probably Weren't Paying Attention When Rsnail Snuck Up Behind Gwin To Steal His Hat, So People Would Thing Gwin Is Not Rsnail. Then, Gwin Gave The Penguin The Autograph And Friend Request, Then The Penguin Walked Away, While Rsnail Slipped On The Water Bucket Below The Shack, And He Dropped The Hat And It Landed On The Puffle. And The Puffle Saw The Stranger (Rsnail), And Ran Up A Tree, For Safety. Then Gwin Saw His Puffle, So He Climbed Up The Shack To Try And Jump On The Tree And Just Then, The Column Snapped, And He Fell In A Pile Of Snow, Not Injured, Because The Snow Was Soft, And He Found Himself Stuck. He Was Covered In Snow, So He Got Suficated, Or He Got Hypnothermia, And Died.

Evidence:

Broken Column
Pile Of Snow
Bucket Of Water

Evidence:

Mickey was killed. Now we need to kill Morgoth. Morgoth wanted to get revenge for something... So he went to the mine. Morgoth asked to see Gwin's hat. Gwin said no. The Morgoth suddenly grabbed Gwin's hat, threw it on top of the mine. Then ran away...
The Gwin went to get it... While Gwin got it, he fell, sliding into the berrel of water, he tripped on the berrel of coal! The coal spilled...
The while he was loosing his balance, he tripped on a berrel that was empty. The berrel fell...
Then Gwin's tripped on the berrel again, not injured, then his hat flew on top of the mine... He got his hat... Then again, his hat fell into the open window of the mine, the Gwin tripped! He fell face down into the cold, cold snow!... Before he did, his leg got trapped on some wood holding the Mine Shack. His leg was so fat, no offence Gwin, that the wood suddenly broke! Then he fell face down into the cold, cold snow...!

Clues:
Open window.
Spilled water.
Spilled berrel of coal.
Fallen empty berrel.

This is the second copy...

Also I found a broken window at the pet shop. Also a missing puffle in the pet shop!

im on the case Mr.Damen.I will find some hacker's etc.

Sorry what I said Sandstorm. I thought you meant the puffle at the forest in the shell. Or did someone say that? I am very confused... Anyway this is a hard mystery. This would be very tough to solve...

Here is the update for my story:

Gwin was just walking along by the mine then a guy thought that Gwin was Rsnail so he asked for an autograph. All of a sudden, Rasnail, or someone else, popped up behind Gwin and grabbed his hat, helment, and put it up on the Mine Shack roof! When Gwin was putting his hat on, the ahat got stuck on the wood things that hold up the Mine Shack. It tore the wood of! Gwin wasn't injured at all. For some reason, he dicided to do a prank on his friends.
He buried himself in the snow and made a tunnel underground that led to his igloo. Before he made the tunnel, he put a real dead penguin in there that looked like him. The he crawled to his igloo. That's what happened...

Evidince:
Broken wood.
Lumps in snow.

There...

My theory: Gwin killed Rsnail.They said Rsnail looked like Gwin.It have actually been Rsnail.But how did he get to the mine?We'll Gwin could have knocked out Rsnail with his bag of puffle food.He dragged Rsnail on top of the mine and broke the roof.He places Rsnail under it to make it look like he fell.Gwin left the island so everyone thought it was him.Thats my theory!
-notrealname2