You leave but still want to see what the problem is

You made it look as if you closed the door, but you actually left it slightly ajar, making it possible for you to look inside. You quickly understood why:

As you looked in, your Mom was already on the floor kneeling in front of Mark, servicing him with her mouth.
"Did she even wait until I was outside before dropping down?" You asked yourself. "She went straight into business. No foreplay, no nothing..."
Then, it hit you. "The whole photoshoot was the foreplay." The worst thing was that you had to witness it.

The camera kept shooting photos in their direction. Mark had her by her hair, which made it seem like he was sending a message: The masculine, dominating figure towering over the feminine, submissive one. One proudly received pleasure while the other one proudly provided it. Each one fulfilling their role and validating each other, taking care in the most intimate way possible between two individuals...

Or at least, that's what you thought before you realized how wild and, for a lack of a better word, hungrily your Mom started slurping his already erect cock. To be honest, how your Mom was behaving took a lot from the dignity and solemnity away that you just described.

Mark, who until now was just letting your Mom attend his shaft with her mouth, spoke:

— Ms. Anon... I'm not going to cum like this.

His voice sounded like a sentence. And it was, because before your Mom could even respond, Mark grabbed her body and threw her on the old fashioned bed they were using for the photo shoot.

Mark leaned over your Mom's neck, letting her feel his weight over her. His breath caressed her skin, making her hair stand up. A smile appearing on her face as he got into position.

Mark directed the tip of his cock at the entrance of your Mom's most intimate place. It wouldn't be fair to say that Mark pushed it all the way in, as your Mom pulled her ass back, just like she did a few minutes ago taking a picture.

Mark held your Mom's waist. He knew she liked it: He realized when he grabbed her hips while posing; he felt how her body shuddered and how quiet she became at once. The only difference was that now he was thrusting his dick inside her for real. Even from your hideout you could hear the plap plap plap his crotch made against her ass with every powerful pump.

Mark's thrusting in this prone bone position went for what felt like an eternity, at least for you. Your Mom seemed to have fallen into that state that overcomes women when they're dicked down just the way they like or need it: She was cock drunk. She partially snapped out of it when she felt Mark's hands on her neck, pulling her face up to kiss him. He murmured something between her lips.

— ...I'm about to cum... — As he preemptively stopped pumping, not wanting to drench the insides of your Mom with his cum as he wasn't wearing a condom.

Hearing this seemed to wake something up in your Mom; she grabbed the sheets, poising herself and started grinding and thrusting her bottom against Mark's waist. She wasn't letting him cum in her. She was seeking it. She wanted to make him ejaculate inside her.

You saw it first in his face. Then in hers. Mark was cumming in your Mom. Raw. Without condom. Your Mom grabbed the sheets even harder, curled her toes and started gasping as she felt Mark’s throbbing dick inside her. Your Mom was orgasming by feeling how her partner was filling up her womb with his seed. The act of reproduction.
That had to be the real expressive result of raw intimacy, like Mark pretended to find out with his project. That'd be a good name. "Raw Intimacy". You had to mention it him later. Maybe he'd like it as title.

They laid there for a few seconds together, exhausted, recovering their breath and trying to organize their thoughts about was just happened. Eventually, Mark pulled back, leaving the warm insides of your Mom, spilling onto the bed some of the "Raw Intimacy Juice" that he just pressed inside her.

Without talking to each other, as if they had somehow made up their mind simultaneously, they started looking for their clothes and getting dressed. When they were done, you heard your Mom's voice calling you to come inside.

You made it look like you opened the door. Mom informed you that they had a long photography session" and they were pretty tired. Basically, they were done and now it was time to go home.