"Just go!" Dean screamed, his green eyes glazed over. It's obvious he has been drinking again- that's the only time he acted like this. He was violent and upset. He always ended the same way: crying in Castiel's arms begging to have Sammy back. He was just a broken little boy who lost his baby brother. It's not surprising he would react this way.
Castiel flinched at Dean's shouting voice as he was told to leave. Dean did this every time he was drunk. He ended up on the bathroom floor, sick and by the toilet, screaming at Cas to leave him alone. Cas had made the mistake once before and one time only. Never again did he leave his baby alone and drunk again. The night Cas left Dean alone, he was sitting on their bed waiting for the green eyed boy to stop crying long enough to stop fighting him. When he didn't hear sobs coming from the bathroom anymore, he walked in only to find Dean, stronger-than-steel, nothing-can-break-me, Dean Winchester in a pool of blood on the floor. He had broken the mirror and slit his wrist open with a shard of broke glass. Luckily, he had gone horizontally and not vertically, meaning if Cas could stunt the blood flow long enough for the emergency responders to arrive, he could save the broken hearted man.
"Dean, listen to me," Cas's calm voice reached Dean's ears just as the sobs began. "You have to stop this. You cannot keep getting drunk every single night to stop hurting over Sam." Dean flinched. That was the first time he'd heard his blue eyed baby brother's name since the accident. He knew, he just knew, it was his fault. John, their father, always told Dean to protect Sam and he had failed. He died because Dean wasn't there on the hunt. He didn't even know Sam had left.
Sam had left to find the vampire nest that had been wrecking havoc on the small town around three am thinking he could take care of the problem himself. He was, obviously, wrong considering about thirty seconds after entering the nest, he was grabbed from behind and his neck was snapped. Dean awoke from a nightmare of Cas, his baby, his little angel, burning on the ceiling above his bed just as Sam's neck was snapped. He glanced over to see his brother's empty bed and a note reading "Gone to vamp nest. Be back soon." Dean literally and actually almost threw up at the thought of hi brother hunting alone and quickly grabbed his gun and pants- in the order. He slipped into Baby, his impala, and sped to the location they'd found the vamps lived at. After an anxiety filled ten minutes and continually calling Sam's phone to no avail, he arrived only to find his brother's body on the front porch of the house and he felt his heart break instantly at the sight of the awkward angle of Sam's neck. Tears began racing down his cheeks as he picked up his brother, put him in the passenger seat and called Castiel, instructing him to met the brother' at their hotel. Cas could hear the tears and pain and heartbreak in his voice but didn't ask questions, only did as he was told.