How long until his heart breaks?

Somethings going to change

At a warehouse
The pack ran into the warehouse chasing Arthur who they had failed to capture.
"Issac you idiot we told you not to move" Derek yelled as he ran next to Issac who was struggling to keep up.
"Well next time tell Stiles not to be holding a giant baseball bat full of nails" Issac yelled back.
"What was I meant to do, hold a butter knife?" Stiles yelled from the back surprisingly keeping up with everyone. Since the evil spirit possession Stiles had been exercising in secret. He went on more runs and had some fighting lessons with a trainer and had actually gained some muscle but mainly wore hoodies and jackets so the pack couldn't tell the difference.
"Both of you cut it out" Scott yelled from the front and ran round the corner to see Arthur had run into a dead end.

Arthur turned around to try and head out but the pack blocked him at every angle.
"Arthur we only want to talk to you" Scott tried to calm the boy down.
"YOU SET A TRAP FOR ME, YOU WERE GOING TO LOCK ME UP" Arthur yelled all stirred up.
"We didn't want to but you wouldn't listen to us. You cannot go around killing people you don't like" Ethan said with his claws out.
Arthur stood their silent watching the pack closely and got his claws out with his eyes glowing a potent blue.
"Arthur we don't want to hurt you" Stiles said in a soft tone to try and calm him down taking a few steps closer to him.
Arthur didn't listen. He looked straight at Stiles and ran towards him ready to attack him.
Derek ran forwards and dragged Stiles away holding his own claws out and pushed Arthur fighting back.
Stiles fell to the ground and watched as Derek fought Arthur more defensively dodging most of the attacks. He was watching intensely when Scott covered his vision and helped him up.
"Why don't you go back to the jeep?" Scott asked but more ordered.
"Why?" Stiles asked as the others tried to get Arthur off of Derek.
Scott pushed Stiles away and went to join the fight. Stiles didn't move. Scott his best friend had just inadvertently told him he was useless. A burden.
He watched as the pack was losing. They were not trying to hurt him when Arthur was going for the kill. Stiles looked down to see he was still holding the nail infused bat. He curled it into his hands angry and watched as his friends were being flung around. As Derek got pushed to the ground Arthur had his claws out high and swung towards his face. It would have connected if it wasn't for Stiles.

Stiles ran as fast as he could towards Arthur and swung his bat right at his chest connecting with his ribs. Knocking the air out of him Arthur stumbled back clutching his had against by the side of the broken window. Stiles who now was not thinking hit him again out of fear for his friends as Arthur had battered them like pin cushions and he wanted Arthur to know how it felt. Arthur fell backwards and unable to grab onto something smashed through the window and disappeared from view.

Everyone gasped and ran forward leaning out of the window. Arthur laid there on the ground, his arms splayed out and eyes wide open in fear with his last specks of blood falling from his nose and onto the floor joining the rest of his blood as it forms a puddle around him.

Everyone looks towards Stiles who held the bat down by his side.
"Stiles you-you threw him out a window" Lydia gasped.
"I didn't mean to. I was-I was just trying to help, you were all not doing well" Stiles started to panic a little.
"Stiles it's okay you did it to protect us" Ethan said.
"You were supposed to stay out of this Stiles what the hell were you thinking" Malia said looking back out the window.
"I'm sorry" Stiles said.
Malia just glared at him. Derek could see nothing good was about to happen.
"Well we need to go before the police show up" Derek called out to everyone "NOW".
The pack tore their eyes away from the dead body and hurried out of the warehouse and piled into Stiles jeep which speeded off into the darkness and away from the nightmare.
Everyone was in silence. No one spoke a word. Derek was the first one to speak.
"Are you okay Stiles?" Derek asked as Stiles kept his eyes firmly in front of him on the road.
"I'm fine" Stiles said.
"You killed a person" Liam said from the back.
Stiles said nothing and remained silent for the entire trip back. He parked his keep and got out. The others followed but only Derek seemed to truly care about Stiles. The others were busy talking about how the murder won't link to them and the sheriff (stiles' dad) would make sure that it would be buried as soon as possible.
Everyone began to go their separate ways and Derek turned around to talk to Stiles but he had already disappeared into the corners of his house.

Back at the Warehouse

A girl emerged from the shadows and rushed out and around the warehouse to Arthurs body. She stood over it with no emotion and bent down closing his eyes then standing back up.

"You got caught. I told you if you kept going the way you were going you were gonna end up dead. Brother you really were a dumbass" she turned around and walked away from the body listening to the sound of police sirens quietly in the distance.