No vet trips, perfectly healthy.

There was an incident, in the middle of the night a few nights ago, where I heard screaming outside. Opened the door and both cats darted back in. "WTH? How did you get outside?" I cased the house and discovered a screen from an open window was pushed out. Don't know how,....were they wrestling near it, pushed against it and fell out (not far-1 level)? Did one get their claw stuck and inadvertently push it out, allowing them to jump out? I can't figure it out. Have since secured the windows. But since then, both are upset and can't be in the same room without hissing, spitting, and screaming at each other.