Corie Walsh, the Illinois woman allegedly obsessed with theLindsay Clancy trial who is accused of killing her 2-year-old son, shared a slew of never-before-seen photos of her child on Facebook before the alleged murder … and one post is downright chilling.

Included in the trove of photos are Christmas Eve pictures of her son Barrett — who Walsh has been accused of murdering — looking terrified next to his siblings wearing matching pajamas.

Walsh eerily wrote in the caption … “PSA: There was no harming of [Barrett] while posing for photos despite the look of sheer terror on his face.”

In another group of photos, Walsh celebrated Barrett — whom she calls Bear in the post — on his birthday.

Walsh said in the caption … “He’s grown leaps and bounds since becoming a big brother but still rests his head on my shoulder, when I’m carrying him up for bed, reminding me of how little he is.”

The sweet posts match the description her former high school friend gave us of the mom … by most accounts, Walsh was “beautiful, kind, intelligent, talented and giving” as a teen.

As we reported … prosecutors allege Walsh planned on killing her husband when he arrived home after allegedly murdering her son.

Prosecutors say Barrett’s body was discovered by two other children who live at the home … and they ran to contact a neighbor.