After Brenda and friends leave, Damon puts the kids to bed. He kills the dog, he has had it and his temper gets the best of him.
He then goes to visit a 'girlfriend' that lives a couple of blocks away. While he is gone, Danielle gets up, finds the evidence (blood, the dog in the trash can by the garage) and runs away.
Damon comes home to find Danielle is gone, the lid is off the trash can.
He gets rid of the dog, maybe he even searches for Danielle, maybe he hopes she will come home on her own.
Brenda,friends come home around 2am. Damon is 'SOMBER'. He is hoping if Brenda doesn't notice, that Danielle will show up and he can claim ignorance.
Unfortunately, someone has picked Danielle up. Someone that likes to pick up little girls. Maybe he talked to her about having just lost her dog.
Next morning, Brenda is awakened by the doorbell, (Damon hopes it is Danielle) but it is the neighbor girl. Brenda finds Danielle is gone, so Damon tells her to call 911, because he already knows.