The black man was taunting with a knife and closing in on the officers. Policemen are allowed to use guns as a deterrent or as a last resort in restraining a running offender, in the event that their life is threatened they are allowed to use lethal force. The officers were clearly inexperienced in dealing with such events and didn't go "by the book". The offender's intention was likely unknown to anybody, it was likely a grudge against the PD of the respective state/county. It's absurd that one would try to suicide in such way while also trying to harm others because most of the times people with suicidal tendencies want to get rid of themselves rather than take another person with them.

The police officers' mistake was unloading two clips of ammunition into him rather than shooting the legs or other parts of the body to stop the offender. It's likely that the offender predicted the police officers would shoot and took the roundabout over the ledge so as to block the first officer by the car door, however it might also be due to the fact that he was sitting infront of the man shooting the video and his friend, so he probably tried to avoid collateral, in which case we could rule this as an act of "suicide by cop". Dead people don't speak however, and my limited information leads me to two possible conclusions.

1) The offender had suicidal tendencies.

2) The offender had a personal grudge against the PD and decided in a fit of rage to intimidate or possibly harm one of the officers.

I don't know how police patrols work in America, but if the same people are assigned to patrols or if there is a pattern in the patrol shifts it's likely that the offender knew one of the officers on duty (although the officers did not look like they knew him) and had a grudge on him.