What is the ruling on fluid that exited in a gush upon seeing a scene that aroused lust, and the person did not know at the time whether it was mani or madhy?

The fluid that exits with a gush accompanied by desire is semen (mani). Semen has three characteristics: it exits with desire, followed by a weakening (of desire); it has a smell resembling that of a palm spathe; and it exits in spurts and gushes. The presence of just one of these characteristics is sufficient to determine that it is semen. Its expulsion in this manner necessitates ghusl (definition) (ritual bath) by consensus of the jurists, if it exits with gushing and desire. If the expelled fluid is not semen, or if there is doubt about its characteristics, then ghusl is not required, and istinja (definition)' (washing of private parts) suffices.