Conversation so far:
What happened to Osceola in the 1830s?
In 1836, Osceola led a small group of warriors in the Seminole resistance during the Second Seminole War, when the United States tried to remove the tribe from their lands.
Did Osceola sign the Treaty of Payne's Landing?
No. According to legend, Osceola stabbed the treaty with his knife, although there are no contemporary reports of this.
How did certain chiefs refusal of the Treaty of Payne's Landing go over?
In retaliation, the US Indian agent, Wiley Thompson, declared that those chiefs were deposed from their positions.
What happened after certain chiefs refused to abide by the Treaty of Payne's Landing?
Wiley Thompson also forbade the sale of guns and ammunition to them.
What was Osceola complaining about?
Osceola, a young warrior rising to prominence, resented this ban. He felt it equated the Seminole with slaves, who were forbidden by law to carry arms.
So did Wiley Thompson giving Osceola a rifle settle the strife then?
No. After his humiliating imprisonment, Osceola secretly prepared vengeance against Wiley Thompson.
Whoa! Was there any blowback from Osceola killing Wiley Thompson?
These nearly simultaneous attacks catalyzed the Second Seminole War with the United States.
Did the US Army respond to Osceola's attack?
These nearly simultaneous attacks catalyzed the Second Seminole War with the United States.
Who won the Second Seminole War?
The United States won with Colonel Worth recommending early in 1842 that the remaining Seminoles be left in peace if they would stay in southern Florida.
What else should I know about Osceola from this time period?
Wiley Thompson considered Osceola to be a friend and gave him a rifle.

Question: Why was he so angry?
Self-contained rewrite: Why was Osceola so angry?