My tenants trim my fig tree to only one 1/4 if its size

[Crystal Shi]

My tenants recently moved out and I found my beloved fig tree(about 20 years old) was topped and cut to its trunk.it is alive and looks miserable. 
my previously tenant also works for me as the property’s gardener( I paid them $70 a month). 
I feel sad for my tree but don’t know what can be done about it. I’m thinking about taking some of the security deposit but don’t know the if it is right.