Able, Baker, and Charlie each operate their own landscaping businesses as sole proprietors.  The three of them were each hired by one client for doing a particularly big job.

The three of them are operating separate lawn mowers to mow a huge parcel of grass.  After doing the job they submitted their bill and the person that hired them refused to pay.

In an act of retaliation, the three of them got together and decided to do some "custom" landscaping.  The three of them took their lawn mowers and mowed down several of the sprinkler heads, destroying them.  The customer sues all of them claiming total damages of $1,000 and assessing each of them 1/3 liability.

The law of joint and several liability in Arizona has been modified by statute and the Arizona Supreme Court has held the statute to be constitutional.  Under the statute, joint tortfeasors can only be jointly liable if they acted in concert to commit an intentional tort.

Does the conduct of the three landscapers qualify to make them jointly liable?  If so, what tort did they commit?  Explain.