My guess is it was a warning shot at Trump.
They’re desperate to get Trump off the campaign trail.
Next they might well plant a bomb or fireworks to kill or wound MAGA supporters. The idea is to intimidate voters. I have read the message—if you want to keep Trump alive, vote for Harris. To save his life, Trump must drop out. If elected he will never finish his term. He better start planning his tomb now. They have an endless supply of wackos who will risk all to kill him and win a place in the history books thinking that they are saving the world from the new Hitler who will round up and send all Liberals to “The Camps.”