In four other tweets fired from Xbox Support account it is confirmed they have got access to Xbox Support twitter account too.
The two tweets fired by SEA account showing access to Xbox Official twitter and Instagram Account,
Tweet from Official Xbox Support team Fired by SEA.
It is possible the Game of SEA is still going on, and few other breaking news can come in few hours.
we have already contacted SEA, and waiting for a response, we will keep you updated with any information on the news.
Short Interview with SEA member over the hack, read from here