Boy Locks Himself in Bedroom; Girl Hysterical

I'm trying to get ready for work. The kids are playing some game, as far as I can tell it's "go in and out of mama's bedroom and make a lot of noise doing it."

Then Sam slams the door shut - on Jo's head.

"WAHHHHH!!!!" she wailed.
"Oh, yes, yes," I say, inspecting the purpling bruise. "It's bad, but I don't think he meant it on purpose."
"YES HE DID, HE DID IT ON PURPOSE, WAH," she continued to yell.

I go to my bedroom to get Sam to come apologize and such - still need to put on deodorant - but no. The door is locked.

"Oh no," I say.
"What IS it?" Jo wails.
"He's locked in," I say.
Jo peels off into more wails. "LITTLE BROTHER, OH MY LITTLE BROTHER," she sobs. The night before, her babysitter had complimented Josephine's huge and impressive lung capacity while singing. "She can really belt it out! She sang for ten minutes!" the sitter said.
She had no idea.

"Sam," I say through the door. "Sam, can you hear me?"
"No," comes a soft squeak.
"Sam," I say, "unlock the door." I say it, even though I know I'm talking to a wall. Well, a door. He's learning a lot of words and concepts these days, but this might be above his head.
"Try to turn the -" Knob? Does he even know what a knob iS?
"Little brother!" wails Jo.
"Josephine, that's not helping," I say.

Now, I wasn't panicking, exactly; but I sincerely did not know what to do. I learned how to jiggle open certain interior door locks with the inside of a pen back when Jo was this age - she loved locking herself in her bedroom. But this particular knob looked very different... just not my area of expertise.

Flashes of a story about myself at this age locking myself in a church bathroom and the possible calls to the fire station came to mind.

"Sam, honey, turn the doorknob," I tried a few times.

And, eventually, he did it.
"I did it!" He exclaimed, rapturously.
"MY HEAD!" wailed Josephine, returning to her initial chant.
"Good lord," I sighed, giving them both a kiss and forcing them - nicely, of course - to hug and apologize.

And that was all before 8 am.