Sorry to hear of your loss. Unfortunately if your son had a screen lock code set, and you do not know the code, the only way to unlock the device is to do a factory reset. This will of course delete the contents, and return the phone back to factory settings. Also, most phones have a security feature which allows for so many failed attempts of entering the code, after which it will automatically do a factory reset.
While the above poster is correct with regard to the passcode, to clarify if you don't know this password the only way to get around this is by doing a factory reset outside of the settings menu to wipe the phone.
By doing this "alternate" factory reset it WILL bypass the security passcode but the phone will then have an activation lock if it is a newer phone from the past couple of years (in addition to wiping all data). This means it will either require the Apple login credentials or the Google credentials, depending on whether it is an Iphone or Android device.
You would then need to provide the proof of purchase to the manufacturer of the device who can then assist you with getting around this activation lock/kill switch so that the device can be used again but you will need to provide the proof of purchase for that to happen.
JENNYL8112, we are truly sorry to hear about your loss. Please allow us the opportunity to explore all of your options in this matter. Chris1060 and lukevinyl provided great suggestions to process a factory data reset to be able to clear all the content from your son's device in order to unlock the device, so it will be available for you to use. If you are not looking to have all the device content wiped from the device we can review other options. Can you please provide us the make/ model of the device so we can properly guide you in the right path?
Follow us on Twitter @VZWSupport
If my response answered your question please click the �Correct Answer� button under my response. This ensures others can benefit from our conversation. Thanks in advance for your help with this!!