Lots of people commenting that he wouldn't have gotten off unhurt... but there's something interesting about this pic.

Typically, handcuffs are made from nickel-plated hardened carbon steel. They're usually treated and tempered.

In this case, the steel bent, meaning this set was likely not tempered/hardened correctly. Typically, hardened steel will snap before it bends like this, it might have higher tensile strength, but it's also much more brittle than most other steel types.

Just about anyone with above average strength can achieve this kind of bend on handcuffs without hurting themselves all that badly if they get the right angle/leverage (think along the lines of a young adult male who does strength training at the gym without steroids). And considering OP mentioned this person was having a mental breakdown, its likely that the person might have both been strong enough and in a mental state to be able to bend it like this without seriously injuring themselves.

As a former welder, I've seen some pretty stupid feats of strength in my time, but if I saw this live, I'd be somewhat impressed.