Did it say what height his is?
The centre of gravity of a human is neutrally the navel. In guys it's slightly higher than ladies (more shoulder, less hip). If he was texting, he would have raised his arms. Each of these things raises his centre of gravity.
He may also have been wearing a backpack. If it had a laptop in it, that's a lot of added mass to raise the centre of gravity.
The grandmother says the rail was waist-high, so he was clearly a tall bloke.
A safety railing only prevents accidental falls if it is higher than the centre of gravity. The population is getting taller, so maybe it is time to raise the limit to account for this.
And as for tripping...
Well most car parks have kerbs, right? Even if not a full pavement kerb, those little ones to stop the wheels getting too close to the walls So it's possible he tripped on a kerb or other obstacle *before* hitting the rail? The article doesn't go into detail.
And, to be fair, it shouldn't HAVE to go into detail. What sort of person reads a news story about an accident and starts publically slagging off the person without full possession of the facts?
What sort of person?
I would tell you, but I think Sarah would be obliged to censor it.