"Angus you were an open soul, with the kindest heart, and you filled every room with laughter," Sydney, who plays Cassie Howard on the series, captioned an Instagram carousel featuring candid photos with Angus. "This is the hardest thing ive ever had to post, and im struggling to find all the words."
Sydney recalled memories of Angus, noting she is grateful for every moment she spent with him.
"You will be missed more than you know, but I'm so blessed to have known you in this lifetime, and I'm sure everyone who has ever met you feels the same," she added. "This heartache is real and I wish we could've had one more hug and 711 run. All my love is with you."
"Words are not enough to describe the infinite beauty that is Angus (Conor)," she wrote on Instagram. "I'm so grateful I got the chance to know him in this life, to call him a brother, to see his warm kind eyes and bright smile, or hear his infectious cackle of a laugh (I'm smiling now just thinking of it)."
On July 31, Angus' family confirmed he had passed away just one week after they buried his father in Ireland.
"The only comfort we have is knowing Angus is now reunited with his dad, who was his best friend," Angus' family said in a statement to E! News July 31. "Angus was open about his battle with mental health and we hope that his passing can be a reminder to others that they are not alone and should not fight this on their own in silence."
Keep reading for more tributes to the Euphoria actor.