Here's the breakdown:
* Deagol found the Ring: While fishing, Deagol discovered the Ring at the bottom of the river.
* Gollum's obsession: Gollum, a creature who lived in the caves beneath the Misty Mountains, became obsessed with the Ring.
* The Ring's influence: The Ring, being an evil artifact, twisted Gollum's mind and desires. It fueled his greed and made him want the Ring above all else.
* Murder: Gollum attacked Deagol and strangled him to death, stealing the Ring.
Gollum's murder of Deagol is a pivotal event in the Lord of the Rings story. It marks the Ring's first act of corruption and sets the stage for its eventual destruction.