Please go to NFL.com and read the rules
The illegal touch was done in the end zone. The player was in the air but the ball was over the plain.
Just like a TD. The player doesn't haven to be in the end zone
There are different rules for the football when it is possessed and when it is not possessed. If the player possesses the ball and crosses the plane of the endzone the ball is in the endzone. If the player does not possess the ball the ball isn't in the endzone until they establish possession. You can't establish possession in the air. It requires your feet to come down in bounds.
Since you want me to reference the rule book, here you go: "The spot of first touching is normally the yard line at which the ball is at when touched. If the first touching occurs while the ball is in the air above or beyond the goal line, and prior to the ball touching the goal line or the ground beyond the goal line, the spot of first touching is deemed to be the spot from which the touching player left the field of play, but in no event inside the receiving team’s one yard line."
Once Weems touches the ball, the play progresses as normal. The kicking team can attempt to recover or whatever. However, regardless of what happens the receiving team can choose to take the ball at the spot the defenders first touched the ball (or any subsequent touch that occurred before a member of the kicking team touches the ball).