You need to file his final 1040 with the IRS and his final state return with Maryland.
If Social Security has been notified, you can even e-file on his behalf.
For more information, follow these links:
IRS
on Deceased Taxpayer
E-file
Deceased Tax Returns
https://turbotax.intuit.com/tax-tips/family/death-in-the-family/L5albFXM4
I am sorry for your loss.
