Compromised account received a massive billing

I received a weird email from aws Singapore to tell me the account is updated which I didn't login for years. I thought it's a scam and ignored the email. After 8 days, I received another email said my account is compromised, Action Required: Irregular activity in your AWS account xxxxxxxxx4704 Amazon Web Services, Inc. no-reply-aws@amazon.com Jun 28, 2022, 8:48 PM (4 days ago) to me Hello, Your AWS Account may be compromised. Please review the following notice and take immediate action to secure your account.

This account compromise poses a security risk to your account (including other account users), and could lead to excessive charges from unauthorized activity. To protect your account from excessive charges, we have temporarily limited your ability to use some AWS services. To remove the limits, please follow the instructions below.

If the unauthorized usage is not stopped we may suspend your AWS account. Failure to contact AWS within five (5) days may also result in the suspension of your account and disruption of your AWS service in order to protect you from unauthorized usage and charges. To further protect your account from excessive charges, we may terminate any suspected unauthorized resources on your account.

Today I received a new email from aws told me my June bill is $160k which is insane. I closed the account immediately without checking the resource usage since it's too scary. Now I think the account is suspended and I cannot response to the ticket anymore.

What should I do to check the account and please please help me about the case, thank you very very much.