I live in Pubic Housing and in 2014 and 2015 a tenant had s…

I live in Pubic Housing and in 2014 and 2015 a tenant had his homeless brother living in the car park in a van. The partner of the tenant would not allow the homeless brother inside the unit or have anything to do with him.
In 2014 he stayed 4 months before I made a written complaint to the Housing Dept and in 2015 it was 2 months before I made a written complaint.
The first time he left in 2014 after calls to the tenant by the Housing Dept. I was abused by the tenant and the homeless brother threatened to kill me.
In September 2015 the homeless brother stayed again. On November 12 11.30 pm he was drunk and on a rampage through the carpark threatening to kill people so I called the police. They came 2 hours later when it was quiet, said a word or two to him and left. I complained to Housing in writing on December 1 about him living in the carpark but they showed little interest. The woman there asked in whose name the van was registered and said she would 'investigate'. I assume now that the van is in the tenants name although he does not have it in his possession or drives it. I received a written reply a day later from Housing that there was no evidence. I asked a neighbour a week later if he had heard from the Housing Dept and he told me that he had received a call from Housing and asked if he knew about a 'disturbance'.
A neighbour I spoke to just a month ago told me that Housing had called her too and asked if there was someone living in the carpark. She told them there was because he was showering under the hose when she came home one night. She then said she had been afraid on the night of November 12. She lives directly above the tenant brother's unit where the fighting was happening and that she does not want to create a problem for herself living there by complaining. I believe he left on that occasion because I went to the carpark at 11 pm on December 3 with my phone with the intention of taking a photo of him asleep in the van. He saw me and closed the sliding door. Next morning he was gone and has not returned as yet.
My problem is that between visits and to this day the rubbish and rotting food is ongoing. A suitcase was left recently in front of my car for weeks. On one occasion manure left by my car door. In April 3 plants I had bought disappeared. One night at 4.30 am in the last month someone was at my front security door. For two weeks I have been able to smell manure around my car but I had been unable to find where it was coming from until the air conditioner was on briefly Thursday the 9th June. Manure or fertiliser has been put in the airvent on the bonnet of the car.
I suspect the tenant brother is doing these things and I do not know what to do about it. I would like to go to the police but without proof I cant see what they can do. My next door neighbour who also had issues with this tenant and my only ally has moved.
Your advice would be appreciated. Thank you Judith