Scream Third Killer Theories

There are many theories that Scream had a third killer and some of the parts that are in question are described below.

Two Places At Once?

There are many situations where it seems that Stu and Billy are occupied, however ghostface is seen. Third Killer? You be the judge. When Randy and Stu are at the video store they see that Billy is there too. But just before that ghostface is seen at the grocery store where Tatum and Sid are. Unless there is a time lapse there is no way they could have been at two places at once.  Another part is when Billy is "killed" and Sid locks him in, but suddenly he appears from somewhere else. Now you could argue that it WAS Stu's house and he knew a shortcut but it is debatable.

Kenny is a heavy guy!

This may seem stupid but think about it. Gale finds Kenny falling off the roof of the van and Kenny wasn't exactly a featherweight. Is it possible that Stu and Billy could lift that man up there? They might have needed the help from perhaps a third killer?

Wait a second, weren't you with Tatum?

It is obvious that two killers were needed in the Casey Becker murder and Stu had reason to kill her seeing that he had dated her,  but at the fountain Tatum says Stu was with her that night. How could he have killed Casey and then been at Tatum's? This one is also debateable seeing that Randy says "Was that before or after you sliced and diced?" He could have done both.

You locked the door, didn't you Casey?

This is really a peculiar part. When the killer continues to threaten and harrass Casey she goes and locks all the doors, which INCLUDES the front door. Yet at the end of that scene the parents simply open the door without unlocking it! I think one of the killers got in the house and then unlocked it for his buddy. Was it simply a mix-up of editing or maybe it was intended all
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