This is my entry into the 100 Day Freewrite Contest, My Father and I both started a story with the prompt, set the timer and then switched stories.
This is the story that I began and 
It was Saturday morning, three days after the event. Margo slowly peeked out the broken glass of the pawn shops front, her heavy breath foggy in the cold winter air.
“Are they still out there?” Asked her sister Florence, holding a bandage to the bloody spot on her leg.
“I don’t see them, if that’s what you mean.” Margo whispered. “That was a stupid move you made back there, you almost got us killed.”
“They were killing that man, what was I supposed to do? Just sit and hide?”
Margo grimaced, thinking back to the burnt in mental image of the man being torn apart. “That is exactly what you should have done.” She hissed. “Even if your little escapade had been successful, in his state, all we would have gained is dead weight.”
“I’m sorry. I was just trying to help.” Florence said, her voice starting to waver.
“I don’t need you to be sorry, I need you to make it out of here alive. If we make it out of the city, we are free and clear.” In truth, Margo had no idea if that was true, but staying there definitely wasn’t an option. As time went on, more and more of the creatures had appeared. Starting with a couple sightings covered on the local news, to dozens of them roaming in packs.
Margo’s reflections were interrupted by a sound from the back of the store. A high pitched squeal came out from the storeroom. Florence jumped to her feet and limped to the back door, peering in through the small window.
She turned to Margo, and the ashen look on her face made it immediately apparent that they’d been found.
“RUUUUUUN!” Florence’s high pitched scream was suddenly drowned out by a loud banging sound at the rear of the store.
Both women turned to the front door and began hurriedly unstacking the crates that they had barred the door with. Once the portal was free, they hurried out into the gloom, with snarls and grunts chasing them.
It appeared that they had been found not only by a stray scout, but by a large roving band. When they reached the center of the street, sounds of approaching death came at them from all sides.