The bigger question is how did the rifle get off the roof and then into the woods. Video of the assassin walking on the roof and jumping down when fleeing shows no indication of the rifle. What happened to it? How did it get down the roof? How did it get in the woods?
Plenty of rifle image in the videos. Minus the easily removable stock, a carbine-length Mauser is only about 32 inches long. Standing, measure from your knee to your shoulder, then slide a 32 or even 40 inch wppden rod under your shirt and upper pant leg. You will have limited hip motion but your knee will function.
Video of the assassin walking on the roof and jumping down when fleeing shows no indication of the rifle.
The video I've seen shows a long, rigid item covered in what is now known to be a black towel. It's easy to see as he gets down to initiate the drop and can be seen again as he lifts it off the roof as he drops. He clearly picks it up on the ground and is seen moving it around as he runs/walks away.
The video is poor quality but, yes, dark shapes indicating the rifle wrapped in a black towel is seen as he clambers off the roof and again when he was walking away.