It wasn't a willful decision. He just did it.
Derek looked down to see the blood oozing down his chest. Staining his shirt even as his whole body seemed to go numb.
"Derek!" Stiles voice sounded wobbly and panicked as he teen barely managed to catch the older man as he started to fall.
Derek managed to make his head lift up and make eye contact with Stiles. He tried to smile but wasn't sure he'd managed it.
"You idiot!" Stiles snarled as he took off his over shirt and balled it up before pressing it against the wound.
Derek couldn't disagree with the statement. "Sorry," he managed to murmur as his body stopped listening to him. He could tell he wasn't healing like he should.
"Why did you do that?" Stiles demanded as he tried to keep steady pressure.
"Instinct..." Derek breathed as his eyes slipped closed and blackness enveloped him.