“I shot a man with a paintball gun just to watch him dye” is a pun on the famous line in the Johnny Cash song “Folsom Prison Blues” (1953),  “I shot a man in Reno, just to watch him die.”
     
“I just shot a man with a paintball gun just to watch him dye” was posted on Twitter by Parasite Hilton on May 5, 2010. “I shot a man with a paintball gun just to watch him dye” was posted on Reddit—Punny on June 5, 2015. “I shot a man with a paintball gun just to watch him dye” was posted on Reddit—Oneliners on September 15, 2015.
     
     
Wikipedia: Paintball
Paintball is a competitive team shooting sport in which players eliminate opponents from play by hitting them with spherical dye-filled gelatin capsules called paintballs that break upon impact. Paintballs are usually shot using low-energy air weapons called paintball markers that are powered by compressed air (nitrogen) or carbon dioxide and were originally designed for remotely marking trees and cattle.
   
Wikipedia: Folsom Prison Blues
“Folsom Prison Blues” is a song written in 1953 and first recorded in 1955 by American singer-songwriter Johnny Cash. The song combines elements from two popular folk styles, the train song and the prison song, both of which Cash continued to use for the rest of his career. It was one of Cash’s signature songs.
(...)
Cash was inspired to write this song after seeing the movie Inside the Walls of Folsom Prison (1951) while serving in West Germany in the United States Air Force at Landsberg, Bavaria (itself the location of a famous prison). Cash recounted how he came up with the line “But I shot a man in Reno, just to watch him die”: “I sat with my pen in my hand, trying to think up the worst reason a person could have for killing another person, and that’s what came to mind.”
       
Twitter
Parasite Hilton
@ParasiteHilton
I just shot a man with a paintball gun just to watch him dye.
9:51 PM · May 5, 2010·TweetDeck
   
Twitter
sorry i dont watch tv
@JonCummingbeard
i shot a man with a paintball gun just to watch him dye
4:48 PM · May 7, 2010·Twitter Web Client
   
Twitter
Yuri Winston
@Snikoggs
“I once shot a man with a paintball gun just to watch him dye.”
7:16 AM · Apr 14, 2011·Mobile Web
   
Twitter
Gnarley Charley
@GnarleyCharley
once shot a man with a paintball gun just to watch him dye
9:49 AM · Apr 14, 2011·Twitter for iPhone
   
Twitter
Karofio
@Karofio
I once shot a man with a paintball gun just to watch him dye. ..
9:59 AM · Apr 14, 2011·DestroyTwitter
 
Reddit—Punny
Posted by u/danlozo June 5, 2015
I shot a man with a paintball gun just to watch him dye.
COMMENTS
indiefolkfan
I now have folsom prison blues stuck in my head.
   
Reddit—Oneliners
Posted by u/danlozo September 15, 2015
I shot a man with a paintball gun just to watch him dye
COMMENTS
velkrosmaak
It’s like a Johnny Cash line, but not.
 
Twitter
Ryan “Fluff” Bruce
@RiffsAndBeards
I shot a man with a paintball gun just to watch him dye.
5:33 PM · Oct 1, 2016·Twitter for iPhone
 
Newspapers.com
12 October 2019, Greenwood (MS) Commonwealth, “Colorado resident becomes famous with funny signs” by Lee Ann Fleming, Weekend sec., pg. 3C, col. 3:
“I shot a man with a paintball gun just to watch him dye.”
     
Twitter
Broken Puppet ☕
@java_assassin
I shot a man with a paintball gun,
just to watch him dye.
9:16 PM · Apr 3, 2020·Twitter for Android
 
Reddit—Dadjokes
Posted by u/VERBERD November 30, 2020
I shot a man with a paintball gun…
....just to watch him dye.