crontab

# mins hours days months weekday
# At 3 p.m. on every 10th day-of-month if today is Monday through Friday, run the shell script
* 15 */10 * 1-5 ./no-way-to-prevent-this.sh >/dev/null 2>&1

no-way-to-prevent-this.sh

# http://wp-cli.org/commands/post/create
# Create a post with the given title and content
wp post create \
--post_title="‘No Way To Prevent This,’ Says Only Nation Where This Regularly Happens" \
--post_content="In the hours following a violent rampage in which a lone attacker killed eight individuals and seriously injured several others, citizens living in the only country where this kind of mass killing routinely occurs reportedly concluded Friday that there was no way to prevent the massacre from taking place. “This was a terrible tragedy, but sometimes these things just happen and there’s nothing anyone can do to stop them,” said resident Firstname Lastname, echoing sentiments expressed by tens of millions of individuals who reside in a nation where over half of the world’s deadliest mass shootings have occurred in the past 50 years and whose citizens are 20 times more likely to die of gun violence than those of other developed nations. “It’s a shame, but what can we do? There really wasn’t anything that was going to keep this individual from snapping and killing a lot of people if that’s what they really wanted.” At press time, residents of the only economically advanced nation in the world where roughly two mass shootings have occurred every month for the past eight years were referring to themselves and their situation as “helpless.”" \
--post_status="published" \
--post_author=2 \
--comment_status=closed \
--tags="satire,gun control" \
--url=theonion.com

This script is a comment about how regularly The Onion posts the story, which is in turn The Onion commenting on how often mass shootings happen in the United States. It happens so often, you could write a cron job to post the story.