The bodies of Short, her 40-year-old husband, Mark, and their three children – 8-year-old Liana, 5-year-old Mark and 2-year-old Willow – were found inside the family’s Sinking Spring home, according to investigators.
All five victims suffered fatal gunshot wounds, according to police. The family’s dog was also shot to death.
It is still unclear who fired the fatal shots and police do not know what sparked the killings, which authorities have called a “tragic domestic incident.” A handgun was discovered near either Mark or Megan, and police recovered a handwritten note from the scene (whose contents they have declined to detail).
Reports have suggested that financial difficulties may have sparked Saturday’s fatal violence – which one relative dismissed as impossible to PEOPLE – and that Megan intended to divorce Mark.
Laurie Swingle McGuinness, Megan’s cousin, wouldn’t discuss a motive with PEOPLE.
“I know what was going on with Megan and Mark, I just don’t know if it’s my place to share her life’s story right now,” McGuinness says. “Yes, there were issues, but I know Megan, and if she felt the need to leave, it’s because she exhausted all other options. Everything she did, she gave it her all. She tried.
“At the end of the day, her kids’ well-being came first.”
Robert McLaughlin, Mark’s brother-in-law, previously told PEOPLE there is a “zero percent chance” the killings were “financially driven.”
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McGuinness says the 33-year-old Megan “exuded beauty and strength her whole life,” even when she learned from doctors that her youngest daughter, Willow, would need a heart transplant.
Willow survived the risky operation, which made national headlines and which was performed the week after she was born.
“As with everything else she did in her life, she was an amazing mommy,” McGuinness tells PEOPLE of Megan. “I never missed a chance to remind her how strong she was – especially over these last few years when faced with unfathomable circumstances regarding Willow.”
Earlier this year, Megan penned an online column about her post-traumatic stress disorder, which she says developed following Willow’s acute health issues.
“Making time to help yourself is a necessity,” Megan reportedly wrote. “We easily recognize the trauma that our children go through, but we need to acknowledge and work through the trauma that we experience as well.”
McGuinness says that Megan was “smart, graceful, and filled with strength” and helped inspire scores of other “heart moms all over the country,” even authoring blog posts she hoped would “help other moms navigate the transplant world.”
Eight months ago, Mark posted a picture of him and Megan on his Facebook page, with the caption, “She’s still the most beautiful girl that I’ve ever met. I’m the luckiest guy in the world to have her as my life and the mother of my three amazing children.”
Going from that moment to now has been devastating: McGuinness tells PEOPLE she is “completely heartbroken that the world lost such a beautiful soul and her beautiful special babies so senselessly.”