You met the friends. So you met them, not they. Similarly, we have Whom did you meet? rather than Who did you meet. The noun friends is the complement of met, so the coreference is made (in traditional usage) with whom rather than who.
Likewise, the shock did not depress me, not I. Similarly, we have Whom did the shock depress? rather than Who did the shock depress?
Now here’s the place where I point out that it is entirely idiomatic today to replace whom by who almost everywhere, with exceptions like the collocation to whom it may concern. Some speakers—and especially writers—do still use whom in all the traditional ways.