It wasn’t the amount of blood that had accumulated all over the floor that convinced James that Regulus was dead.
Or the fact that Regulus had stopped the gurgling and wheezing noises several minutes ago as he drifted into cruel stillness.
It wasn’t Barty’s tear stained and blood splattered face. Or Evan’s desperate attempts to shake Regulus awake. It wasn’t even Peter’s sorrowful look upon checking for a pulse. Or his frantic attempts to do CPR anyway.
It was Sirius’ agonised wails as he pleaded and called out to a God he never believed in to spare his brother. To bring him back. “I just got him back,” Sirius screamed. “I just got him back. Please. Don’t do this. Please bring him back. I just got him back.”