As mentioend below, the initial huge selling volume in afterhours did not take index below this week's low. The subsequent drop below this week's low was on light volume , and now another set of light buying volume is taking place to move index back above this week's low.
These small volume afterhour moves not very meaningful. Given the magnitude of the tariff annoucement today, we could expect heavy trading volume tomorrow in normal trading hours, and whether market can hold this week's low will be very important to watch