Please write a termination letter to Ms NAME_1 who worked in HR.
Take this as an example: Dear Mr NAME_2,

I’m sorry to inform you that as of 12/3/2018, you’ll be no longer employed with Acme Inc. As discussed, the reason behind this is your reduced performance the past six months. We made this decision after the end of your Performance Improvement Plan, which we launched on 07/03/2018.  

From Dec. 3 on, you won’t be eligible for any compensation or benefits associated with your position. Please return your swipe card, company cell phone and laptop by 5 pm on Dec. 3 to our HR office.

You are entitled to your salary up until Dec. 3 and we’ll also compensate you for your remaining vacation days. We’ll also provide severance pay that will amount to two monthly salaries. You’ll receive a separate letter with the complete compensation details and information about your health coverage (as per Consolidated Omnibus Budget Reconciliation Act or COBRA).

Please keep in mind that you have signed a non-compete, non-solicitation and non-disclosure agreement. If you have any information about our customers, employees or other stakeholders stored on paper or on your personal devices, you must delete it immediately.

If you have questions or clarifications, I’m at your disposal until the end of next week.

We wish you best of luck.

NAME_3