As soon as his back is turned, Columbine is making out with Harlequin. So when he catches them at it, Gaston Séverin as Pierrot strikes her as Harlequin flees. Of course, he's terribly sorry when he thinks she's dead, and drinks.
Pierrot is derived from Italian commedia dell'arte in the 17th century, and became popular in France, where he typified the sad clown figure. As he continued on into the 20th century, various schools of artists attributed various interpretations to him, but clearly he was considered High Art of a sort.
In this one, he's a rather foolish sort of character appealing more to sympathy than to anything funny.