You left a channel
{
"type": "channel_left",
"channel": "C024BE91L"
}
The channel_left event is sometimes sent to all connections for a user when that user leaves a public channel. It is sometimes withheld.
Clients should respond to this message by closing the channel — this means that when a channel is left from client A, it will automatically be closed in client B.
In addition to this message, all existing members of the channel will receive a
channel_leave message event.