DEFINITLY GET A LAWYER.!!!.
No Ifs or buts bro. I have been to court several times as witnesses for alot of friends. THe ones with Lawyers won. The ones without did not.
Get a lawyer.
Also Im not a legal professional, and really don't like lawyers myself, but I have 3 on retainer cause, well, just cause, and well leave at that.
Good luck to you though.
I don't understand how an attorney is going to help much, even though I'm sure most will charge you a retainer just to speak with them.

The tenant was on a 10-month lease and is now, as contracted, on a month-to-month lease.
The property owner would like him to commit to a longer lease for his peace of mind while he is away travelling (not that his reasons will make any difference)
If the tenant does not want to commit to a longer lease, he has the choice of moving out, just as the property owner has the freedom of choosing a tenant that is willing to commit to a longer lease since the 10-month period is over and both owner and tenant are only contracted for 1 month at a time.
There are 2 choices.
1) Commit to another, long lease.
2) Seek another place to live.
Calling the police was a bit over the top, especially since the landlord did not enter the actual domicile.
This should be a good object lesson on how to deal with a situation in a professional, businesslike manner, rather than ignoring it.