After the news broke that Avicii had died, Kačerová shared the above slideshow clip to her Instagram page which features photos of her and the 28-year-old with her son.
There are photos of the two napping together, playing in the sand by the ocean, and one of Avicii teaching the young boy to play piano.
Additionally, there are photos of all three spending time together like a family, along with the caption, "The brightest stars burn out the fastest."
In a series of separate posts on her Instagram page, Kačerová shared a letter she wrote which expresses her feelings about her former flame and his death.
Speaking directly to the DJ, Kačerová wrote, "Dear Tim, I've spent the last days waiting to wake up, waiting for someone to tell me this is some sick joke, some awful mistake. I think it's finally settling on me now that I will truly never get to see you again."
"I used to tell you that Luka will never remember a life without you. Now I hope that he will remember his life WITH you. I'll be there to remind him. I'll show him."
"Every time I think about something we won't finish I feel physical pain in my heart. We never finished the Harry Potter marathon - we had the last one left - you never witnessed me having a meltdown when Snape dies," she added. "I never finished persuading you that our daughter's name MUST be Serafina. You never finished your tattoo sleeve in which the inner forearm would have a face coincidentally resembling mine."
"I was always very set on keeping our relationship private because I wanted it to be OURS and ours only and wanted no part in that madness. But I thought, if I'm going to share this with the world, it will be when I'm pregnant with our child. Ohhh how that plan went awry," Kačerová's letter continues. "I called you baby angel. Little did I know how soon you would become one. The last words you ever said to me were 'I love you.' Well I LOVE YOU. As much as you love Mexican Coke... and then some."
It is mentionable that Kačerová made a comment about their "daughter" in her letter, though there is no indication that she is currently pregnant. It may simply be a reference to a conversation the couple had about possibly having children in the future.