Two men are murdered on Memorial Day 2015, but who is responsible?

Sources:

https://www.nbcsandiego.com/news/local/slain-father-of-7-considered-hero-in-community-family/53818/

https://www.sandiegouniontribune.com/sdut-homicide-investigation-valencia-park-two-dead-2015may26-story.html

https://www.nbcsandiego.com/news/local/joel-branch-jr-gerald-morris-valencia-park-unsolved-murders/107366/

https://www.nbcsandiego.com/on-air/as-seen-on/dave11525_san-diego/16459/

https://www.sdcrimestoppers.org/blog/two-year-anniversary-of-the-unsolved-murders-of-joel-branch-and-gerald-morris