Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
I'm sorry about your loss. You can easily reset the password ***** booting into Mac OS X Utilities screen. Follow the steps below;
Turn off your Mac.
Turn it back on and immediately hold down Command and R keys at same time for 10 seconds.
This will boot your Mac to "Mac OS X Utilities” menu.
Click on the “Utilities” menu in top bar and select “Terminal".
Type (without space) : resetpassword
Press return. This will Reset Password ***** Select the hard disk at top column, select the user account from the drop down under it, confirm the user account and then change password ***** Save. Then click on the Apple icon and select Shutdown.
Turn it back on. After restarting, if you get any message about Keychain then click Create New Keychain. If you are still getting keychain error, then reset the keychain access database. Follow the steps below to reset Keychain;
Open Keychain Access, which is in the Utilities folder within the Applications folder.
From the Keychain Access menu, choose Preferences.
Click General, then click Reset My Default Keychain.
Authenticate with your account login password (the password ***** reset earlier).
Quit Keychain Access.
Please let me know if that didn't work, so we can continue troubleshooting.