Can air rifles kill people

If the psi is turned up too high, there's a regulation limit.

---------------- new answer--------------------

In the USA there is no regulation limit. However in Canada and the UK there is. In the US you will find that there is a large selection of PCP air rifles that are charged to 3000 PSI and fire a 50 caliber pellet. These PCP class air rifles are capable of bringing down a Boar and Yes they can kill you. Even the smaller ones can kill you.

PCP=PreCharged Pneumatic

(See the link below)

Airsoft air rifles are designed to not kill you and are considered toys but do hurt.