Vandalism - how to prove whodunnit!

[Amanda Thompson]

Hi friendly landlords! I have a beautiful picnic table with "I <3 Jai" and a penis carved into it. 

This is a community of 12 higher end townhouses. It is one year old, and over the past year everyone has been good neighbors without much issue. The end unit, next to the gazebo/picnic area just got 3 new tenants. A neighbor texted me to let me know these tenants have had a group of guests (around 8-10 people) over the past few nights and they've been hanging out in the gazebo at the picnic table. After each night, there has been trash left all over the gazebo. The first morning after the guests, "Jai" was carved into the table. The 2nd morning after the guests, the rest of the carving was present. I have never found trash at the gazebo, and I've never even seen anyone use it.

Is this enough to charge the tenant with a fine and replacement of the table? The neighbor who told me about this said there were some of the guests hunched over the table for a little bit. I don't consider this neighbor nosey... she's really good about communicating with me if there are issues since she lives in the house at the end too (directly across from these new tenants). 

It is expressly written in the lease that vandalism of any kind is a violation, as well as tenants are responsible for their guests' actions.