How did the killer enter?

Hint 1 of 16:

Well, there was no forced entry on the door.

Hint 2 of 16:

And the stairs are incredibly creaky, so no one could have crept up them
without someone knowing.

Hint 3 of 16:

So maybe they didn't get into Robner's room via conventional methods.

Hint 4 of 16:

Really, the other possible entryway is pretty obvious.

Hint 5 of 16:

Check out the rug in Robner's room.

Hint 6 of 16:

Mud, huh?  Maybe the killer had their shoes in some mud.

Hint 7 of 16:

Now look at the balcony.

Hint 8 of 16:

Look at the railings.

Hint 9 of 16:

Scratch marks!  So, someone must've climbed up!

Hint 10 of 16:

There's some more evidence to be found, though.

Hint 11 of 16:

Look at the ladder in the shed.

Hint 12 of 16:

There's mud on the ladder, suggesting that it was put somewhere in the mud.

Hint 13 of 16:

About 11:30, talk to McNabb about what's bugging him (Type MCNABB, WHAT'S
WRONG?).

Hint 14 of 16:

Ask him to show you the holes.

Hint 15 of 16:

Follow him and look for the holes.

Hint 16 of 16:

Could it be possible that this was where the ladder was placed so someone
could climb up onto the balcony?