Mr Free owns a YouTube channel called Slo Mo Guys, and Ms Turney is a popular cosplayer.
The couple managed to call police as Giles, who was armed with a handgun, smashed a window to gain access to their home, waking them in the early hours of January 26, a local news station reported.
Giles, who had driven 11 hours from New Mexico, returned to his car where he was confronted by police. He opened fire on the cops, who shot him dead.
Police said "it was apparent that Giles' sole intent was to cause harm to someone who resides there".
It was reported that Giles had "developed a fondness" for Ms Turney, but disliked her boyfriend Mr Free.
Police later searched Giles' home and mobile phone where they found more evidence of his obsession with Ms Turney.
Police found several notes in Giles' phone referring to Ms Turney and her boyfriend Mr Free by name. He was reportedly jealous of their life and success.
Court documents stated: "Threatening thoughts were recorded by Giles and directed toward Gavin Free, i.e., 'I want Gavin Free to die alone, with no children.'"
They also found evidence that Giles had been planning the "burglary and homicides of Megan Turney and Gavin Free" at his home. The search revealed Giles "was an avid player of video games and was known for watching YouTube videos".
Mr Free has since tweeted his thanks to the Austin police for their quick response.
"Hey everyone. I just wanted to say thanks for all the support and concern regarding the recent incident,' he tweeted on Monday. "It's been a rough time for Meg and myself the last few weeks but we are doing OK.
"I want to give a huge thanks to Austin Police for the amazing response time."
Ms Turney added: "Thank y'all so, so much for each and every kind message today and a special thank you to the Austin Police for their quick response that night and their ongoing support during this difficult time. Heart you guys so much."
