Yeah, Dogg
Instead of leaving a tiny note, it is sometimes preferable to use the entire windshield to convey the message. The majority of the time, people would look at a note and throw it away without reading what was on it. The person who sought to punish this driver was not willing to take that risk.
They used a bold marker to inform the car owner that parking in their spot will not be tolerated any longer. While the use of the term “dogg” is usually friendly in nature, we take it that this person was trying to convey a serious warning—possibly a threat.