Matrix visual tooltip to show values

I have a table of elements such as:

Each person can have multiple categories. From this table I have managed to create a matrix like this:

In order to achieve this (with help from this forum) I used the following Measure to aggregate the numbers:

I am now struggling with trying to create a tooltip that shows the Name (or ID) of the people in each cell, i.e. I want to create something that liiks like this:

The mock up file is attached below:

https://www.dropbox.com/s/i2wrw6zowwjzxs0/Cross%20matrix%20example%20post.pbix?dl=0 

I would be very grateful for any help.