I would also try the police they might do something as well to protect the children.

Check the rents and stop by the Police department and share the address, so they can tell you about crime in the area.

You need police reports and court convictions.

Also, it goes without saying that you should consult an attorney; Okay briefly reading over your lease agreement, it's a good agreement but it is very loosely written and does not provide for many remedies prior to eviction so... that is something you should look to improve on moving forward, there should be an escalation of force in as $XX fee until rectafied and THEN otherwise eviction, also you should number your lease clauses.Regarding the current situation first and formost, I understand you live in the property as well but you should certainly take on a 'HANDS OFF' approach in regards to internal disputes amongst Tenants; you are after all a landlord, not the ethics police nor the real police.... if other Tenants have issues such as those they should inform you and then they should contact the police... if it's not police worthy than it is more than likely just internal bickering. 

I then visited the local police substation and fire department.  

Area is in somewhat high crime but there is a police station right across from it.   

I confronted him on lying about it and said he could meet my project manager and we can call the police to make a deposition.

I know I'm a disqualified person since I'm a linear descendant.

If you do catch them, pressing charges and getting police to do anything is next to impossible. 

If you are set on having rentals in high crime areas, I recommend trying to house police officers.