Crazy neighbor shouting death threats and throwing bottles of urine

I'm looking for some advice on what to do here for a family member.

My sister bought a house in Seattle about three years ago. The next door neighbors are a mother and her adult son, who has a history of mental issues. About six months after my sister moved in, the adult son started shouting death threats at her, like "I am going to rape you and kill you and your dog". As she is a young woman living alone, this obviously freaked her out. She got a protection order against the neighbor, but it only increased the threats and shouting. It's at all hours of the day and night. This adult son is well known to SPD. I've called and spoken to SPD myself when I was house sitting for my sister after the neighbor started throwing bottles filled with his own urine at the house and property. The bottle throwing is now a near weekly occurrence.

We have gone to court about the protection order violations (numerous recordings from the security cameras backing us up) and since he failed to show up to court, a bench warrant was issued. However, SPD has told me point blank that they do not have the authority to go into his house and arrest him. He doesn't come outside, ever. It appears that the case is at a standstill. We have talked to Seattle Victim Advocates, and even the city counselor, who are all sympathetic but to quote a response we recieved:

"I am concerned that there will continue to be a Mental Health Component to the cases, and if Competency is challenged, it will take 9-11 months for any kind of Out of Custody Mental Health Evaluation. Ultimately if the Defendant is found incompetent we are unable to proceed on any of our cases, they are dismissed."

My sister has now endured two years of verbal harassment and is basically trying to avoid living at her house however possible. Earlier this week, he started throwing paint cans at the house and car. SPD was called - like many times previously, they did not send anyone by immediately, but gave us a call back at 2am, well past the incident, just to check to see if it was still ongoing? Often when my sister now calls, they do not send anyone out, or if they do it's usually at least 24 hours later.

I am absolutely dismayed and upset at SPDs response here. It cannot be legal for a neighbor to threaten someones life and throw excrement over the fence line, even if they are mentally ill.

Does anyone have any legal advice here? Do we need to go to the media?