TLDR: Family friend bought a house. Previous owner had tenants living month-to-month in house with no lease. Tenants given 120 days notice that house was selling and family friend taking full possession of property. Friend has taken possession and they refuse to leave. What can my friend do?!

A family friend just bought their first home. The previous owner had tenants in the home who had a 1 year lease that had expired and were living there month-to-month. Previous owner asked for 120 day closing to help their tenants find somewhere to move.

2 days before closing my friend requests his final walk through. Still a few things here and there but house is mostly empty.

Closing day comes. My friend/their lawyer get keys and the deed and they go to move in. Surprise! Tenants say they are now squatting and refusing to leave. They are extremely confrontational to my friend who had no idea they were still there. From what we could see through the front door they had moved their belongings back in.

My friend wants to avoid serious confrontation with these people for fear of reprisal/damages to the home. I want to stake the place out, wait until these people leave for work, change all the locks, and throw all their stuff in a dumpster. What can we do?