You should first find a statement for the 401k somewhere in your her files. That statement should have a phone number and address. The first item of business is to verify with the employer Human Resources/Personnel who the beneficiary she designated is. Beneficiary(ies) are the only authorized people who can do anything with the 401k. Once the beneficiary is known - they can work first with the employer HR and ultimately with the 401k plan company about receiving the 401k money. You would transfer the money into a NEW IRA in the name of (EACH) beneficiary (your new IRA company should help with that designation - just be sure they understand this is inherited money). Also, understand that each beneficiary MUST take at least the minimum distribution (called Required Minimum Distributions, or RMD) each year until all the money has been taken out. If you're confused - find a fee only adviser at www.NAPFA.org as a disinterested third party for guidance.
There is one added piece of data you may want to have. You did not indicate whether your son’s mother died while still working. If so, her company may send the assets to the named beneficiary without advising that person. It all depends on the rules if the company. I blogged about this. http://korvingco.wordpress.com/2014/06/24/401k-distribution-after-death/
"There are two rules that apply to an after-death distribution. One of the two must be used in all cases. The first allows for payments to be made within 5 years of the death of the participant. The second option allows a benefactor to received payments through his or her lifetime on a regular basis."
First of all, my condolences. I am not sure how old your son is. If he is of age, then he could do this, but otherwise, you could do it on his behalf or the executor/administrator of the estate can do it. You will need a certified copy of the death certificate.
The way 401Ks usually work is that there are beneficiaries listed who inherit the 401K. Your son may or may not be one of the beneficiaries. Let's assume that your son is one of the beneficiaries. You will need to send proof of the death to the custodian of the plan. Assuming the 401K is all pre-tax money which is tax deferred, your son will owe income taxes if the money is distributed directly to him from the plan. Your son may have the following choices, depending on the plan document:
1) Take a lump sum distribution and pay income tax on it. 2) Leave the money in an inherited 401K and continue taking taxable distributions (assuming Mom was taking distributions). 3) Roll the money over to an inherited IRA at another institution and take distributions over 5 years, paying income tax over the 5 years. 4) Roll the money over to an inherited IRA at another institution and take taxable distributions over your son's lifetime. 5) Roll the money over to an inherited ROTH IRA at another institution. Your son will pay tax on the entire amount right away, but the money can continue to grow tax-free over his lifetime. Your son will have to take yearly tax-free distributions.
If you have a statement from the 401K, then you can call the 800 number and talk to someone at the custodian. If you don't, then you will need to call the HR department at Chart Industries, explain the situation, and get the correct number to call. Tell the custodian about the death. They will require you to send in a certified copy of the death certificate. They might send you an inheritance package which explains what you can do and what your options are. They will also require your son to prove who he is.
Note that if this is a taxable estate for either State or Federal estate taxes, then your son may owe estate taxes on the amount he inherits, depending on how the will is written.
I don't know the family dynamics, but someone should be appointed administrator/executor of the estate. That person is usually identified in the will. If there is no will, then I suggest that the most likely person to be the administrator in the family, goes to Surrogates court in the county where she lived and asks to be appointed estate administrator. The Surrogates court is usually very helpful and you might be able to do this without a lawyer with their help. If the estate is over $100,000 or if there are other complexities, then you might want to get a good estate lawyer to help you.
Please contact the HR person at the company. Hopefully they can provide you with enough information from the beneficiary form and from the record-keeper/TPA that will get you taken care of. I would ask a local advisor or someone you know that has familiarity with these situations to help you. It is probably worth a small fee to have a fee for service advisor assist you with the appropriate steps to take.