[SPOILERS FOR SEASON 2!!]
You had walked into Alastor's swamp-like room and noticed how he looked, hunched over his dresser with his shirt unbuttoned halfway and his bowtie undone. He was currently smoking a cigarette, which he usually only did when he was stressed or agitated, and drinking a glass of some strong liquor while you began pestering him to let you help him with the barely-closed-up wound on his chest.
It was healing very slowly and his microphone staff thing was still not fixed. He was clearly unhappy about both situations and feeling vulnerable, as reflected in his strained smile and his deer-like ears being pinned back against his head.
As a result, he was not dealing with a lot of people very well. He had abandoned most of his duties at the hotel and had begun snapping at you, which is very rare since you were one of the very few he trusted.
"I said no!" He growled, finally snuffing the cigarette out in the ashtray on his dresser and starting to button up his shirt again.
He hated feeling weak and needing or relying on other people.