At the very end of the clip, we see Aria in what looks like Spencer’s house. She screams as someone in all black (presumably “A” ) comes out of nowhere and grabs her. We'd yell that loud too if we were attacked!
We’re guessing the attacker is Ian (Ryan Merriman) because the summer premiere is called "It’s Alive," and it makes sense that he would suddenly appear to scare the girls. But then again, it could be anyone, maybe even one of his accomplices.
Poor Aria, let's hope she survives the accident without too many injuries.