Seven things happened at once:
The Vampire broke the sealing spell on the portrait of the fat lady, and entered the common room.
The Fat Lady started screaming her head off.
Several students fled into the dormitories.
Felix Ohfman appeared behind the Vampire, and started using spells.
Dumbledore came out of the fire, and strode to help Ohfman.
James pushes Lily, Cindy, and Lydia back as the vampire flashed his eyes towards them. It broke through the spells and went straight for the group, but James wouldn't let this happen.
He pulled his wand right between it's eyes, then shouted a spell. The vampire flew back a bit, stunned. Them the older professors handles the vampire. James let out a sigh of releif.
"Well, Professor Atticus McLaren ~??~ was attacked by a Vampire, and he has escaped our custody.
The other is...Headmaster Dippet.....is dead...." said Dumbledore sadly, looking at the floor, and clutching himself as if he'd been stabed.
"You are all to stay here tonight, until we have a hand over the situation.
Good night! Board the windows, put out the fire, and we will close the portrait again.
Miss Lydia, please come with me."
Lydia looked at Dumbledore. She sighed and nodded. She knew she could not refuse him. Although he was only a professor he possesed an ability that made everyone like him and comply to his suggestion.
Lydia glanced at James then to the boys dormitory wishing Lupin was there. She silently followed Dumbledore out.