Can a devil ray's sting kill a person?

Yes.

On September 4, 2006, television personality Steve Irwin was pierced in the chest by a stingray barb while snorkeling in Australia and died shortly after.

https://en.wikipedia.org/wiki/Stingray

But that was a freak accident, is it common that devil rays kill people?

Dasyatids generally do not attack aggressively or even actively defend themselves. When threatened, their primary reaction is to swim away. However, when attacked by predators or stepped on, the barbed stinger in their tail is whipped up. This attack is normally ineffective against their main predator, sharks.

Depending on the size of the stingray, humans are usually stung in the foot region. It is less likely to be stung by brushing against the stinger. Surfers or those who enter waters with large populations of stingrays have learned to slide their feet through the sand rather than stepping, as the rays detect this and swim away. Stamping hard on the bottom as one treads through murky water will also cause them to swim away. Humans who harass stingrays have been known to be stung elsewhere, sometimes leading to fatalities.

Same link as above:

https://en.wikipedia.org/wiki/Stingray

If the question is "Can...," the one example proves it can.
If the question is "Do most humans stung by a devil ray die?" the answer would be "No."

A devil ray is a particular kind of ray, the manta.
This article is interesting and mentions the Tampa baseball team. These animals would rarely be encountered by humans.
https://en.wikipedia.org/wiki/Manta_ray

According to Wiki, Steve Irwin was killed by a bull ray, which I suppose to be the Australian bull ray.
https://en.wikipedia.org/wiki/Steve_Irwin
https://en.wikipedia.org/wiki/Australian_bull_ray

I have personally known three individuals who were stung by stingrays of another family. The stings were intensely painful and one victim nearly died of a secondary infection, but they all recovered.
http://www.potamotrygon.de/fremdes/stingray%20article.htm