There's been 2,829 mass shootings in America over the time span of those 4 attacks.
So that would make trans people responsible for 0.14% of them.
Not surprising that Elon Musk is amplifying this though, his lurch towards far right politics in America was started by his own daughter coming out as trans and cutting off all contact with him. I wonder how she feels seeing him promote this kind of hateful rhetoric.